Three elderly Kenyans have won an historic legal victory over the British government after the high court gave them permission to claim damages for the grave abuses they suffered when imprisoned during the Mau Mau rebellion.

The court rejected the government's claim that too much time had elapsed for there to be a fair trial, just as it threw out an earlier claim that the Mau Mau veterans should be suing the Kenyan government, not the British.

The government's lawyers accepted that all three were tortured by the colonial authorities. They suffered what their lawyers describe as "unspeakable acts of brutality", including castration, beatings and severe sexual assaults.

After the ruling, the Foreign Office acknowledged it had "potentially significant and far reaching legal implications", and said it was planning to appeal.

However, an estimated 2,000 other Kenyans – the survivors of more than 70,000 Mau Mau suspects who were imprisoned during the seven-year insurgency in the 1950s – are now expected to come forward to sue the British government.

Many more men and women around the world who were imprisoned and allegedly mistreated during the conflicts that often accompanied the British retreat from empire may also be considering claims. A number of veterans of the Eoka insurgency in Cyprus in the 1950s are known to have been watching the Mau Mau case closely.

Friday's ruling came after a series of legal battles over more than three years. Paulo Muoka Nzili, 85, Wambugu Wa Nyingi, 84, and Jane Muthoni Mara, 73, were originally accompanied by a fourth claimant, Susan Ciong'ombe Ngondi, who died two years ago, aged 71.

Mr Justice McCombe said a fair trial was possible and highlighted the fact that thousands of documents had been found in a secret Foreign Office archive containing files from dozens of former colonies.

Last year the judge had said there was "ample evidence even in the few papers that I have seen suggesting that there may have been systematic torture of detainees during the Emergency".

Martyn Day, of the veterans' law firm Leigh Day, said: "This is a historic judgment which will reverberate around the world and will have repercussions for years to come. We can but hope that our government will at last do the honourable thing and sit down and resolve these claims."