The British government accepts that colonial forces in Kenya tortured and abused detainees during the Mau Mau rebellion, the High Court has heard.
Three elderly Kenyans who are suing the government for damages were told it did not dispute that "terrible things" had happened to them.
Their lawyers say it is the first ever official acknowledgement by the UK.
The revolt against British rule in Kenya in the 1950s and 1960s was marked by atrocities, with thousands killed.
The British government argues that too much time has passed for a fair trial to be conducted.
Before starting cross-examination of witnesses at the trial, the QC for the British government, Guy Mansfield, said he did not want to dispute that civilians had suffered "torture and ill-treatment at the hands of the colonial administration".
He spoke directly to each of the witnesses, saying he did "not want to dispute the fact that terrible things happened to you".