Archbishop Desmond Tutu has called on the British Government to show "magnanimity and compassion" towards elderly Kenyans fighting for damages over alleged colonial atrocities during the Mau Mau uprising.
In a letter to Prime Minister David Cameron he accuses the Government of continuing to refuse to deal with "these elderly torture victims with the dignity they deserve".
He adds: "It is high time that the British Government showed some magnanimity and compassion."
Two letters sent by Tutu to the Government in February and this month were released by lawyers for the three Kenyans at the centre of the case as the latest round of their legal battle was about to begin.
A year ago they won a "historic" ruling which took them one step nearer to achieving their goal when Mr Justice McCombe said they had "arguable cases in law".
The fresh hearing at London's High Court will focus on the Government's argument that the claims cannot proceed because they have been brought outside the legal time limit - but lawyers for the Kenyans will argue that it is an exceptional case in which the judge should exercise his discretion in their favour.
In the February letter to Mr Cameron, Archbishop Tutu accuses the Government of "relying on legal technicalities in response to allegations of torture of the worst kind".
During the two-week hearing, the court will consider evidence about events in detention camps during the 1950s from Jane Muthoni Mara, Paulo Muoka Nzili and Wambuga Wa Nyingi.
The court has heard that Mr Nzili was castrated, Mr Nyingi beaten unconscious in an incident in which 11 men were clubbed to death, and Mrs Mara was subjected to appalling sexual abuse. The claims are being brought with the support of the Kenya Human Rights Commission and the Kenya government.
Solicitor Martyn Day, senior partner from law firm Leigh Day & Co, said: "Desmond Tutu has today firmly called on the British Government to deal with these elderly victims of torture with the dignity, compassion and magnanimity that they deserve. We leave the door open to the British Government to meet with us to resolve this claim even at this 11th hour."