Four elderly Kenyans who claim they were tortured by colonial officials and soldiers during the Mau Mau insurgency in the 1950s have won the right to sue the British government for compensation.
Without deciding whether there had been systematic torture of detainees, the judge, Mr Justice McCombe, ruled they have "arguable cases in law".
The decision is a setback for the Foreign Office, which has argued that the UK government should not be answerable for any abuses committed by the former British colony and that liability had devolved to the present Kenyan government.
Of the five original claimants, one has already died. The remaining four – Wambugu Wa Nyingi, Paulo Muoka Nzili, Ndiku Mutwiwa Mutua and Jane Muthoni Mara – are mostly in their 80s.
They allege brutal treatment in detention camps, including castration and sexual assaults at the hands of British colonial officials and soldiers. Other detainees interned during the Mau Mau uprising, it is alleged, were murdered, forced into labour, starved and subjected to violence from guards. Among those allegedly abused was Barack Obama's grandfather.
Previously unseen evidence of atrocities emerged during the case when colonial-era files withheld from the National Archives were discovered by historians working with the claimants' lawyers.
In dismissing a Foreign Office application to strike out the legal action, McCombe said: "I have decided that these five claimants have arguable cases in law and on the facts as presently known, that there was such systematic torture and the UK government is so liable."
He described the UK authorities' attempts to avoid responsibility as "dishonourable" but accepted that before a full trial, the issue of whether the injuries were sustained too long ago – beyond any legal time limit – would have to be argued at a separate hearing.
"It may well be thought strange, or perhaps even 'dishonourable', that a legal system which will not in any circumstances admit evidence obtained by torture should yet refuse to entertain a claim against the government ... for that government's allegedly negligent failure to prevent torture which it had the means to prevent, on the basis of a supposed absence of a duty of care."
Elsewhere in the judgment he said: "There is ample evidence in the few papers that I have seen suggesting that there may have been systematic torture of detainees during the [Mau Mau] emergency.
"The [documents] evidencing the continuing abuses in the detention camps … are substantial, as is the evidence of the knowledge of both governments that they were happening and of the failure to take effective action to stop them."
The case has been supported by a large number of human rights groups and prominent international figures. Archbishop Desmond Tutu, who has urged the British government to deal with the Kenyan victims honourably, said: "Responding with generosity to the plea of the Kenyan victims is not a matter of legal niceties. No, it is about morality, about magnanimity and humaneness, about compassion."
Welcoming the judgment, Martyn Day of the solicitors Leigh Day and Co, which represented the Kenyan survivors, said: "It is an outrage that the British government is dealing with victims of torture so callously. We call on the British government to deal with these victims of torture with the dignity and respect they deserve, and to meet with them and their representatives in order to resolve the case amicably."
Day said that even if the next hearing ruled too much time had passed for a full trial, "a lot of the evidence about what happened will be put into the public domain and people will be able to judge for themselves".
The Foreign Office minister for Africa, Henry Bellingham, said: "We understand the pain and grievance felt by those on all sides who were involved in the divisive and bloody events of the emergency period in Kenya.
"The government will continue to defend fully these proceedings given the length of time elapsed and the complex legal and constitutional questions the case raises. Our relationship with Kenya and its people has moved on since the emergency period."
Mau Mau uprising
The Mau Mau uprising was a revolt mainly by the Kikuyu people in Kenya against British colonial rule. It was suppressed with brutal security measures, including the execution of more than 1,000 convicted rebels.
In response to the uprising, a formal state of emergency was declared that lasted from 1952 until 1960. British regiments were drafted in to support the local King's African Rifles.
In an attempt to control areas outside Nairobi, a policy of forced "villagisation" was introduced. By 1955, more than a million Kikuyu people had been removed from their homes and relocated inside barbed wire compounds that were patrolled by armed guards.
The officially accepted death toll for the period is around 11,000, but many historians suspect the true figures were far higher. The overwhelming majority of victims were native Kenyans rather than white settlers.
David Anderson, professor of African politics at Oxford University, has estimated the death toll to have been as high as 25,000; Caroline Elkins, of Harvard University, suggests it could have been up to 300,000.
The extent of the atrocities has begun to be acknowledged as colonial-era files, discovered in a government storage depot at Hanslope Park, in Buckinghamshire, have emerged. They are now in the process of being transferred to the National Archives.
Two of the techniques regularly used by security forces were "screening", or interrogation; and "dilution", the use of force to extract co-operation from suspects. In one camp, Hola, the beatings are believed to have left 11 detainees dead.
"courtesy the guardian-U.K"