Ten Kenyans detained during the Mau Mau independence uprising 50 years ago are seeking compensation in British courts for alleged atrocities.
One of the men, Mucheke Kioru, says he was tortured, starved and beaten while in a British-run detention camp, where he was held for smuggling food and weapons for rebels.
British officials said the Government would contest the case vigorously. Lawyers say that if the claim is successful it will open the floodgates to thousands who claim they also suffered.
"My life was ruined," Mr Kioru said, recalling the day, as a 23-year-old labourer, when he was rounded up and detained for four years without charge during Operation Anvil in 1954, a brutal military offensive launched by Britain to crush the Mau Mau uprising. He said he was forced to stand neck high in water for days at a time; had raw sewage pumped into his body - contracting typhoid as a result - and was severely beaten. He was left in constant pain and suffering frequent nightmares. The British also confiscated his family's farm, he said.
Kenya's Human Rights Commission believes 90,000 Kenyans were executed, tortured or maimed during the crackdown and 160,000 were detained in appalling conditions.
"This was a dark period in British history," said Martyn Day, a British human rights lawyer hired by the Kenyan Human Rights Commission to represent the Mau Mau veterans.
He believes the case could also have implications for the US over its role in Iraq, Afghanistan and the treatment of prisoners at the US detention centre in Guantanamo Bay, Cuba.
Mr Day will lodge the case at the High Court in London on 20 October - a Kenyan public holiday marking the beginning of the uprising when 180 independence leaders were seized. Legal papers will also be served on the British Government claiming the UK was responsible for atrocities during its rule. Judges are expected to fix a date for a legal hearing.
It is not clear that Britain can be sued so long after the alleged abuses. Charley Williams, a spokeswoman for the British embassy in Kenya, said all claims of government responsibility were passed to the Kenyan government at independence. "We would defend the case in this matter vigorously although we would wait to see the details before deciding on what approach we would take."
If the case does go to trial, among those who will give evidence is the American academic Caroline Elkins, author of the 2006 novel Imperial Reckoning: The Untold Story of Britain's Gulag in Kenya. She said: "The British tried to cover up systematic abuse and have to take responsibility for what happened." But she warnedthat it was a "political hot potato" that could raise tensions in both countries.
Mucheke Kioru, 75, lives in a one-room wooden hovel and works as a watchman guarding a small farm for a wage of £7 a month.
"I fought for freedom only to be shackled by poverty, nightmares and to die a lonely old man, unable to have a wife or children," he said. "That is my legacy of independence."