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."
Mr Day says that the claimants want an apology and a Mau Mau welfare fund to ensure that they, and their fellows, can live with an element of dignity in their final days.
When Mr Justice McCombe gave his ruling last year, he emphasised that he had not found there was systematic torture in the Kenyan camps nor that, if there was, the UK government was liable to detainees, such as the claimants, for what happened.
Opening the case for the Kenyans, Richard Hermer QC said that the crux issue was whether a fair trial was still possible.
He argued that the existence of thousands of official records and other sources of primary contemporary documentation meant a fair trial was possible, despite the passage of time and the death of certain witnesses.
If the court came to such a conclusion, it should apply the "greatest caution" before shutting it out - not least because the claims concerned allegations of severe torture and because it had already held that the claimants had reasonable prospects of success, he said.
There was no doubt that the passage of time would have a material impact on the overall quality of evidence but there was still a vast amount of high quality evidence covering every aspect, particularly since the release of the Hanslope archive.
There were comprehensive records of key decision making at all levels of government plus committee minutes.
The evidence also came from a wide range of different sources where allegations could be checked, cross-checked, corroborated and so proved or disproved.
Mr Hermer said that, although key decision makers were no longer alive, high quality witnesses had been identified who were, and who could be traced.
It was far from certain, he added, that the Foreign and Commonwealth Office did not still possess relevant documentation which was potentially of high probative value, as it was assessed that 40% of the Hanslope materials had been received.
Mr Hermer said that it had always been acknowledged that the task was going to be painstaking and time-consuming.
He told Mr Justice McCombe: "It is going to take a long time, cost a lot of money and occupy court time. All that gives rise to notions of proportionality.
"But, in a case of this importance. after a finding rejecting a strike-out application, the complexity, length and cost of the case should not impact on the exercise of your discretion."
He said that both civil and criminal courts in this country had long experience in dealing with historic cases fairly.
The Foreign and Commonwealth Office (FCO) says that the court should not exercise its discretion and make an order dis-applying the time limit which would otherwise operate.
"It would be contrary to principle and the balance of fairness to allow this matter to proceed to a trial. There cannot be a fair trial of the issues," said Guy Mansfield QC.
A trial of issues said to have continued for seven to ten years with changing personnel, relationships and policies would present a major task for the court even if the events were relatively fresh, the documents well ordered and witnesses with reasonable recollections readily to hand.
"After so long it is simply impossible", said counsel in written argument.
He said that the FCO faced "irredeemable difficulties" in respect of the availability of witnesses and documents in defending the claim.
It would have wished to call those in senior positions in the Colonial Office, War Office, British Army and the Kenyan Colonial Administration - but the majority of those who might give material evidence were now dead.
"Without those witnesses, and indeed with the necessarily limited recollections of those who do survive, the very complicated and difficult task of determining the competing factual positions cannot be fairly conducted."
He added: "There is a dearth of evidence which can be given as to what was in people's minds when they made decisions and sent or read telegrams or attended meetings or were told of matters or visited places.
"We do not know why they did what they did or conversely did not act in particular circumstances. Minutes of decisions are often just that. They do not explain matters further."
The hearing was adjourned until tomorrow when the claimants are expected to start giving evidence.