Murdered, missing, imprisoned in camps...The guns may be silent in Sri Lanka for the first time in 26 years, but the price of peace for the innocent Tamils caught up in the fighting could not be higher ... Dan McDougall travels from the Tamils' UK protest in Parliament Square to the killing fields of Sri Lanka

A foul-smelling monsoon closes in from the north, carrying dark clouds of ash from the Hindu funeral pyres burning along the "Highway for Peace and Unity". At the roadside, translucent glasswing butterflies flutter and dance in the charred iron shell of an old British Leyland bus, its undercarriage ripped apart and shredded like paper by a Claymore landmine.

Little more than a cratered strip of asphalt running 100 miles due north from the ancient city of Anuradhapura to Jaffna, the road's grandiose Marxist title is typically deceptive: today it bisects a dramatically transformed landscape - the broken heart of Sri Lanka's former Tamil Tiger country, a battle-scarred route lined with thousands of shallow graves, unexploded landmines and the rotting stumps of palmyra trees blackened by the rain.

Here, sheltering from the darkening skies at a remote army checkpoint, a group of weary teenage soldiers gather around an old Russian television impassively watching the capital, Colombo, celebrate the end of the war.

Dressed in messianic white, the Sri Lankan president, Mahinda Rajapaksa, is walking through the streets of the capital as followers shower him with pink flower petals. At each street corner he is offered traditional kiribath (milk rice) and kavung (oil cakes). Crudely dubbed over the footage, hastily assembled songs declare "Our King Rajapaksa", wishing him "Ayubowewa" - a long life.

"We won the war, we won, OK!" shouts an army NCO in coarse Sinhalese, breaking the silence and ordering the young soldiers on to a personnel carrier heading north. "Now get back to work."

At their journey's end, no more than 30 miles north along the single-track road, the conscripts will be brutally confronted with more than a quarter of a million personal hells - Tamil refugees who have fled the Sri Lankan civil war in recent days and weeks, as the secessionist Liberation Tigers of Tamil Eelam (LTTE) fought and lost a brutal endgame for a separate Tamil state in the country's northeast. Malnourished and traumatised, the displaced stare out from behind the barbed wire of internment camps erected by the Sri Lankan government.

Elderly grandmothers, infants, pregnant women, wounded fathers, their faces as twisted and contorted as the razorwire that imprisons them, trapped in a state of incarceration the Colombo authorities claim is necessary for the refugees' own "safety". Further into the bush are the field hospitals, hidden from the eyes of the world yet overflowing with civilian victims of the war. Beyond the medical camps, according to eyewitnesses, are thousands of freshly dug graves. Six thousand miles away in London, a growing body of UK-based campaigners are calling it quite simply "The War Without Witness".

"The British government doesn't give a fuck about Sri Lanka, they just don't give a fuck, nobody here does." The British Tamil student's anger peaks as he is marched across Parliament Square in central London by his girlfriend, his fists, his entire body shaking with grief and loss as he waves a photograph of a bloodied child, much of her stomach missing. "Is it a relative?" I ask. Nobody seems to know. In his fury the young man lets go of the deathly image, and is forced to chase it down in the breeze.

Another Tamil woman, middle-aged, an NHS nurse in faux ruby earrings, holds up a photocopied print of her missing sister for the photographer, pauses, and breaks down, lost in chest-racking sobs. Nobody consoles her. Everyone stands back. Blinking in the sunshine, the others are drowning in their own private grief. Most of them wait patiently, portraits of their loved ones in their hands, their own stories of horror at the forefront of their minds. Behind them a crowd is gathering, their number is growing. To reach our impromptu studio, each has passed by a wooden hut erected in the heart of the square where hundreds of passport photographs of the dead and the missing have been posted. Some are gory. Bodies decapitated, dead eyes staring out. Beneath each photograph are contact numbers for concerned relatives.

It had started as a simple idea in the dreary hotel room in Colombo that I was sharing with photographer Robin Hammond. As the lights of the old port twinkled below and Sri Lanka heralded a new beginning, I read an Amnesty report that ranked Sri Lanka second in terms of numbers seeking asylum in the UK. Tamils in Britain, largely thanks to a mass exodus in the 1980s, now number approximately 200,000, mostly in south and west London.

So I sent an email home, asking a few London-based Tamils I knew had been affected by the war if they would pose for portraits when we returned. The replies, within 24 hours, were staggering. "We have 50 and can get you 500 more," said one source. "More can come at short notice," said another campaigner. "How many do you need? We have thousands of photographs, missing, dead, children, grandmothers, this is a genocide, what do you expect?"

I shouldn't have been surprised. An organised and galvanised diaspora, who haven't slept in two months, as the battle to end all battles raged on the island that bore them - all of the UK's Tamils have been affected by the war.

While the expenses scandal has gripped British political life in recent weeks, Britain's Tamils have taken over Parliament Square. Over a month ago, one of the protestors, Prarameswaran Subramaniam, lay down on a fetid mattress opposite parliament and went on hunger strike. His ultimatum was simple:

"I will stay here until either my body can continue no longer or the British government persuades the Sri Lankan government to stop shelling my people," he said. Subramaniam began his protest at the end of April after discovering that his mother and several siblings had been killed in Sri Lankan military attacks. He is now recovering in hospital.

Other UK-based Tamils threatened to throw themselves off the top of Big Ben or drown themselves in the Thames; two actually made it into the water but were rescued by a police boat patrol. In response to the Tamil takeover of Parliament Square, Westminster council complained about their numbers and moved to protect the grass, which they claimed was going through an "urgent reseeding". The Times accused the Tamils of turning Parliament Square into a "shanty town", a banner headline that particularly irked the Tamil diaspora - professors, doctors, school teachers, engineers and architects among their number.

In the Commons, the Speaker of the House, Michael Martin, condemned the actions of some Tamil protesters, who, he claimed, put young children "in the way" of police officers. Conservative MP Gerald Howarth raised a point of order to ask what powers the Speaker had to order the Metropolitan Police to secure "free access to Parliament" for MPs. He said: "It is completely outrageous that members of this House have been subjected to this inconvenience, that the people of London have been subjected to this inconvenience. The situation in Sri Lanka is nothing to do with this House. Surely law and order has broken down outside the Houses of Parliament." Not surprisingly, Howarth's stance provoked fury among the new occupants of Parliament Square.

As he unfurled a peace banner in Parliament Square, Tamil campaigner Prakesh Mano, 36, told me: "Britain is to blame for this; like Palestine, like Zimbabwe, your history has a hand in the death of innocents in 2009, and the British government should stand up and take ownership of it - and you are more worried about some overpaid politicians not being able to get to work?" It is a view of history held by most Tamils, who believe that Sri Lanka's substantial Tamil minority once had their own autonomy in the north before the British Empire turned the whole island into the colony of Ceylon. Britain, they claim, then handed Ceylon's Sinhalese majority rule and independence in 1948 as a single entity, without enshrining the rights of the Tamils to their own land and language.

Krishna Ruban, another protester, said: "This is a war without witness. The media is cut off from what is really happening in Sri Lanka. A genocide is being hidden from the world." He then added: "London-born teenagers who have never even been to Sri Lanka are marching with their grandparents. This is about brothers and fathers and sisters being killed. I know people who have lost 15 members of their family. It is not just here - there are demonstrations in France, Germany, Holland, Switzerland, America and Canada. It is literally everywhere."

According to the UN, more than 8,000 civilian refugees were killed on the Sri Lankan battlefield this year, mostly in the past three months in a government-designated "no-fire zone". There is also mounting evidence, including testimony from those who escaped it, to suggest that army bombardments were mostly to blame for this. Some, although fewer in number, have also accused the LTTE of shooting at them to try to prevent their escape.

On 25 May, the United Nations Human Rights Council convened a special session on Sri Lanka, following a request submitted by Germany on behalf of 17 mostly European countries. Its members proceeded to vote down a proposed resolution decrying the Sri Lankan government's disregard for civilian life. But another draft resolution tabled by the Sri Lankan government itself, praising its own commitment to human rights, was passed by a vote of 29 to 16. Its supporters included China, Cuba, India, Russia, Pakistan and Egypt.

By effectively welcoming the "liberation" of tens of thousands of the island's citizens from the grip of the Tamil Tigers, the UN made no mention of the shelling of civilians and kept silent on the desperate need to allow the Red Cross and other humanitarian groups into the camps where some 300,000 Tamil civilians have been interned.

Navi Pillay, the UN High Commissioner for Human Rights, insisted that there still needed to be an inquiry into "very serious abuses", yet Sureen Surendiram, of the British Tamils Forum, said that the UN was paying lip service to the civilised world, again. Human Rights Watch and leaked UN documents recently suggested the death toll was closer to 20,000, with many of the dead women and children, he said. "And now the Sri Lankan government is holding our loved ones in massive internment camps, the likes of which we haven't seen since the Second World War." He added: "The fighting may be over, but retribution killings are being carried out in the camps. Our people are also starving and dying from lack of medical help."

The Lonely Planet guidebook says the beach at Uppuveli is the most beautiful on Sri Lanka's east coast. As the sun sets it certainly looks like an island paradise, a curve of white sand with palm trees and deep emerald water. If you drive through the jungle in the east, you can see errant herds of wild elephants crossing the road. Long-tailed monkeys watch nervously from the trees. At night, fireflies hang by the roadside. This is the Sri Lanka tourists flock from around the world to see, but along the road to the town, hundreds of soldiers line the road, looking nervously into the jungle. Despite the war coming to an end, fear of last-gasp Tamil Tiger suicide attacks cuts to the core of every soldier here in the northeast. On closer inspection, Uppuveli's beach is littered with sewage and rubbish, its hotels boarded up. No tourists come here any more. The jungle, long burned by government soldiers trying to clear the roads of hiding places for Tamil Tiger guerrillas, is a twisted and charred wasteland.

Here in the Sivananda Thaovanam Orphanage, more than 100 children huddle together against the pounding rain outside. The children's eyes betray the tragedies they could not easily put into words. Each child has his or her own story, but they all have one thing in common: their parents were killed in the war. Four-year-old Mohanapriya's eyes light up as she speaks about her parents, telling us how she is waiting for them to come and take her home. "She is too young to understand they are gone," says one of the orphanage directors. "What can we say to her?"

The orphanage is threadbare, like its inhabitants. The room which serves as their bedroom, a communal hall with peeling paint and a few lockers with broken locks, overflows with second-hand clothes and toys that have seen better days. The only bed is piled high with mats, sheets and pillows. Despite its woeful lack of facilities, Sivananda Thaovanam has been a safe haven for 240 children for four years. Twelve-year-old Theverajah Kajenthini cries as she remembers the day she lost her mother. Trapped on the frontline of the war, a Sri Lankan government shell ripped through their home, killing her sister, her aunt and her mother. Several months later her father, accused of being a Tamil Tiger sympathiser, was executed by "unknown forces". "I don't understand what has happened to me," she says. "Like the other children in here we don't talk about the past. I am old enough to know my parents are gone but the younger children laugh and play and tell us their mums and dads are coming back. Many of the children in my village became orphans during the fighting. I can't deny what happened to me. I saw my mother's body. She was on fire after the shelling and died of burns to her face and neck. Her head was black, it was the last I saw of her."

Across the north of Sri Lanka, hundreds of orphanages such as this house are the legacy of Sri Lanka's 30-year civil war, the orphans cast adrift like flotsam. Most remain traumatised. With no funding for rehabilitation or counselling, their fates seem to be sealed at a tragically young age. Most are introverted and prone to intense periods of grief and depression. They all live a bleak and meagre existence.

"The camps to the north of here are full of children like me, I am told," says 11-year-old Mahetevan Suganya. "Tamil boys and girls like me who cannot escape. At least I have my friends here in the orphanage and I can walk in the garden and play with my toys. The director tells us all we are fortunate to be here and to be protected from the war. I don't feel particularly lucky. I feel angry and upset at what is happening to me."

In the corridors of power in Colombo, the hard-won victory over the Tamil Tigers would have been savoured by one family above all: that of the Sri Lankan president, Percy Mahinda Rajapaksa, who carved out victory with the help of his brothers, Gotabaya, the defence secretary, and Basil, who largely masterminded the political and diplomatic strategies that accompanied the war effort. The brothers, members of a prominent political family of Sri Lanka's Buddhist Sinhalese majority, won through utter ruthlessness. In contrast to previous Oxbridge-educated leaders, they had no links to the English-speaking elite of Colombo and showed few qualms in severing Sri Lanka's ties with the west in favour of strengthening relations with China and Russia - countries that supplied sophisticated military hardware and diplomatic muscle.

In giving the cold shoulder to Britain and the United States, the president also won the approval of ultra-nationalist Buddhist monk MPs, who had demanded victory at any cost over the Tigers and on whom Rajapaksa depends for his parliamentary majority. In 2006, a year after he became president, air, sea and ground assaults were launched against rebel strongholds in the north and east. The army nearly doubled in size to 180,000 men in two years and began to adopt guerrilla tactics, using the Tigers' own methods - sending in death squads to kill rebel leaders. Now the president, a lawyer who worked as a film actor and library clerk before entering politics, enjoys messianic-like status in the country he rules with an iron fist. Many Sri Lankans feel he has deliberately blurred the genuine grievances of the Tamil minority - a community that has been oppressed since it lost its favoured status with the end of British rule - with the atrocities carried out by the terrorist Tigers over 26 years. They also suspect that a new period of persecution and oppression of the Tamils will emerge with a victorious Sinhalese government.

As I travelled across Sri Lanka, President Rajapaksa, basking in victory, declared the final defeat of the Liberation Tigers of Tamil Eelam (LTTE) in a speech to his parliament on 19 May. But more than 30 opposition chairs in the 225-seat chamber were vacant. Members of the Tamil National Alliance, the largest group of parties representing the Tamil minority in the north and east of the island, had refused to take their seats. It was a reminder of an unhappy and uncomfortable truth: the Tamil Tigers may be finished as a fighting force, but the bitter ethnic divisions that fuelled the 26-year war live on.

Some hours later, as I walked the streets of the Sri Lankan capital, state television aired footage of the dead Tamil Tiger supremo, Velupillai Prabhakaran, the back of his head missing from what was undeniably a summary execution, a cloth covering the top of his skull, which appeared to have been blown off. Prabhakaran's Tamil Eelam once existed as an unofficial nation within a nation, a state that ran on a different time zone (Indian time), had its own police force, jails, judicial system, and semi-extortionate system of tax collection. Everywhere across Tamil Elam flew the Tamil Tiger flag: a roaring tiger backed by a pair of crossed Kalashnikovs, pouncing with claws bared from a cartoonish explosion. Walking through Wellawetta, a predominately Tamil district of Colombo, nationalist Sinhalese flags flutter from every Tamil home for fear of Government reprisals. In a dark corner of the slum suburb a scrawl of graffiti quotes an adapted Indian proverb: "Do not blame God for having created the tiger, thank him for not giving it wings."

"You can't go down that road. You shouldn't have come this way," the soldier bellows, first in Sinhalese and then in English, his hand menacingly stroking the nuzzle of the rifle splayed across his chest. I look at his bony black fingers - he is pointing east towards the coastal town of Pulmoddai and the road we have just travelled down.

"How did you get here from there? It is a dangerous route and you are a target for terrorists." Behind our interrogator I recognise a parked Alvis Saracen personnel carrier, its adapted gun turret trained on our minivan. As we speak three other soldiers come out of a small hut. The tallest flourishes a revolver and demands we hand over our passports. He then disappears to make a call. I'm convinced after a series of close shaves we will finally be arrested, possibly beaten, certainly deported.

"We are tourists and we are lost," I explain, without prompting. In the back of the van, in the stitching of the carpet, we have hidden digital memory cards and a small notebook, the only record we have of a refugee camp we stumbled across 20 miles to the north. Our presence there, to witness the incarceration of around 6,000 Sri Lankan refugees, had sent the camp directors running for their satellite phones. On Sri Lankan radio, government-sponsored adverts have called on the nation to effectively "finger" foreigners trying to head north.

Behind the barbed-wire fence at the Pulmoddai camp, tiny children had stared out at us, open-mouthed, their eyes sunken and hollow, the first signs of malnutrition. Around the camps, scarcely functioning mothers and grandmothers waited patiently for brown trickles of water to emerge from the earth. The inmates were surrounded by a cordon of steel: dozens of Sri Lankan soldiers sitting at 10-yard intervals around the perimeter of the compound, their weapons cocked and trained on their captives.

It had taken a 13-hour drive along dangerous roads and past a dozen heavily militarised checkpoints to get this far. At every corner the Sri Lankan military, which has effectively created a border across the entire country, cutting off the north of the island to foreigners, tried to intimidate and stop us, brandishing weapons and forcing us back at each turn.

Brought down by ship from the frontline 50 miles to the north, the Pulmoddai refugees before us are effectively prisoners of war - their plight among the first evidence of an attempt by the Sri Lankan authorities to inter stricken refugees in dozens of camps across the north of the island. To the north, hundreds of thousands more share a similar fate, and the looming threat of deadly disease and malnutrition.

Along the hard road to the Pulmoddai refugee camp is heard the sound of hammering and the clink of metal. Before our eyes Sri Lankan soldiers hammer huge wooden stakes into the ground to create another perimeter fence to "imprison more refugees". Beside the road lies thousands of yards of razorwire fencing. "More are coming," says a locally recruited engineer drafted in to help build an access road. "They are coming from the front, perhaps tens of thousands more, for the long term. Each hole in the ground stretching into the far distance over there is another stake to imprison them."

It is closing in on midnight. A police siren breaks the stillness of the summer evening as a handful of weary Tamil protesters begin packing up for the night, folding banners and neatly packing flyers and posters with red elastic bands. Their organisation and attention to detail is meticulous; there is little money for more flyers, and those they have left over for another day are precious - each thin piece of paper a witness statement from their families and loved ones.

A young Tamil student returns to the square after scouring the bins in the streets around Westminster, retrieving the crumpled and folded flyers nonchalantly discarded by passers-by. "Did they stop to look at these?" he cries, pointing to a crudely photocopied photograph of a dead child cradled in his father's arms.

Some of the protesters will take the trundling night bus to Neasden and Wembley, and home to their extended families. Others, who have come down from the Midlands, will share hostel rooms or sleep rough in the backstreets sweeping down towards the Embankment, avoiding CCTV cameras and police patrols, before returning to their placards and rainbow banners at dawn, tramping bleary-eyed over the grassy heart of democratic Britain.

Many of the Tamils here have abandoned their jobs to make their stand. Karunakaran, 28, files through a shoe box of belongings and pulls out a dog-eared passport photo of his younger brother. He nervously fingers the Kavala, the sacred Hindu red string wrapped twice around his wrist.

"He is dead, my brother; this is what my head says, but there is still hope in me that he is lying in a hospital somewhere, fighting for his life, making it through for me and my mother. There are so many trapped in the camps and they are unable to get messages to the outside world. People are scouring websites and the news for a glimpse of their parents or their brothers. It's the uncertainty that kills you slowly. You see their faces in your sleep, you wake up at night and cry, wondering where they are, if they are suffering, if they are starving to death, if they are in prison being tortured or cast out to sea in a boat."

As he speaks Karunakaran produces a pile of paperwork from a file. At the head of the most recent document from Eaton House Immigration Service in London the words "Liability to Detention" glare out bleakly from the page. "I've been in Britain for 10 years but the immigration authorities are now telling me it is safe for me to go back to Sri Lanka," he says. "My sister was killed, my brother and cousin are missing. They are telling me to go back, and I'm not the only one. Your country gives me the right to protest here on Parliament Square, but your government is also intent on sending me back to a land where those same protests will lead to my death."

Taming the Tigers

1972 Armed with just a revolver, Velupillai Prabhakaran forms a Tamil militant group, which eventually becomes the Liberation Tigers of Tamil Eelam (LTTE)

23 JULY 1983 LTTE ambushes an army patrol, killing 13 soldiers in the Jaffna peninsula and sparking anti-Tamil riots elsewhere that leave around 600 people dead

8 JULY 1985 Sri Lanka opens first direct talks with Tamil guerrillas. They fail

29 JULY 1987 India and Sri Lanka reach agreement on the deployment of an Indian peacekeeping force

24 MARCH 1990 India loses 1,200 troops at the hands of the LTTE, and withdraws to leave the Tigers in control of large parts of northern Sri Lanka

21 MAY 1991 Indian prime minister Rajiv Gandhi is assassinated by a Tamil Tiger suicide bomber

1 MAY 1993Sri Lankan president Ranasinghe Premadasa is assassinated by a Tiger suicide bomber

2 DECEMBER 1995 The Sri Lankan army captures the Jaffna peninsula

8 OCTOBER 1997 The United States declares the LTTE a foreign terrorist organisation

25 JANUARY 1998 An LTTE suicide bomber devastates Sri Lanka's holiest Buddhist shrine, the Temple of the Tooth, killing 17 people

FEBRUARY 2001 Britain outlaws the LTTE as a terrorist organisation, followed in 2006 by Canada and in 2007 by Australia

DECEMBER 2002 At peace talks in Norway, the government and rebels agree to share power, with the minority Tamils enjoying autonomy in the mainly Tamil-speaking north and east

3 MARCH 2004 Renegade Tamil Tiger commander, V. Muralitharan, known as Karuna, leads a damaging split from the main rebel movement

2 NOVEMBER 2007 The head of the Tamil Tigers' political wing, SP Thamilselvan, is killed in a government air raid

2 JANUARY 2008 Sri Lanka withdraws
from a ceasefire deal and steps up attacks against the Tigers

2 JANUARY 2009 Sri Lankan forces capture Kilinochchi, leaving the Tigers only the jungle district of Mullaittivu

14 APRIL 2009 The Tamil Tigers say they are ready to negotiate a ceasefire and restart peace talks. The government refuses, ordering them to surrender

20 APRIL 2009 Tens of thousands of trapped civilians manage to flee from the shrinking area still under rebel control

13 MAY 2009 For the first time, the United Nations Security Council asks the warring parties to spare civilians

16 MAY 2009 President Mahinda Rajapakse says the rebels have been defeated

17 MAY 2009 The Tamil Tigers concede that the battle "has reached its bitter end" and that they have "decided to silence our guns"