LONDON  - Three elderly Kenyans began a court battle Monday to win damages from the British government for brutality they claim they suffered at the hands of colonial officials during the 1950s Mau Mau uprising.

The two-week hearing at London’s High Court opened a year after a British judge ruled that Jane Muthoni Mara, Paulo Muoka Nzili and Wambugu Wa Nyingi could sue the government over allegations including castration and torture.

The trio’s lawyers say Nzili was castrated, Nyingi severely beaten and Mara subjected to appalling sexual abuse in detention camps during the bloody Mau Mau rebellion against British colonial rule.

“We are pleased that finally our clients will be able to tell the court their story,” their solicitor Martyn Day said ahead of the hearing.

“The British government has thrown everything at these claims in an effort to derail them on technicalities.

“We are confident that justice will be done.”

A fourth claimant, Ndiku Mutwiwa Mutua, has died since the High Court ruling in July last year that the test case could go ahead. The British government argues that the claims cannot proceed because they have been brought outside the legal time limit. But the Kenyans’ lawyers, who are bringing the claims with the support of the Kenyan government and Kenya Human Rights Commission, argue that it is an exceptional case.

The hearing will have access to an archive of 8,000 secret files that were sent back to Britain after Kenya became independent in 1963.

Opening the case for the Kenyans, barrister Richard Hermer said the existence of thousands of official records meant a fair trial was possible, despite the passage of time and the death of some witnesses. “It is going to take a long time, cost a lot of money and occupy court time,” Hermer warned, urging the judge not to let this influence his conclusions given the seriousness of the allegations.

But the government argues that after six decades, a fair trial would be impossible, and that many of the senior colonial officials it would have wanted to call as witnesses have died.

“It would be contrary to principle and the balance of fairness to allow this matter to proceed to a trial,” said lawyer Guy Mansfield.

The claimants, who are in their 70s and 80s, are due to begin giving evidence on Tuesday.

Their lawyers say they want an apology and a welfare fund to ensure that around 1,000 surviving former detainees can have some dignity in their old age.

More than 10,000 people died during the 1952-1960 Mau Mau uprising, with some sources giving much higher estimates of the number killed.

Tens of thousands were detained, including US President Barack Obama’s grandfather.

But when judge Richard McCombe ruled last year that the Kenyans could sue the government, he stressed that he had not found evidence of systematic torture in the Kenyan camps.

South Africa’s Nobel Peace Prize laureate Desmond Tutu has written to Prime Minister David Cameron accusing Britain of neglecting its human rights duties over the case.

The retired archbishop said Britain’s unwillingness to make amends is “strongly out of step with many other modern democracies that have been faced with historic allegations of abusive conduct”.