Thousands of files from former UK administrations are to be released by the government, including documents about the Kenyan Mau Mau uprising.
The publication coincides with a High Court compensation case brought by four Kenyans over alleged human rights abuses in the 1950s and 1960s.
Thousands were put in camps by the British during the uprising, and many were tortured or killed, say activists.
The government says too much time has elapsed since the alleged abuses.
London law firm Leigh Day & Co lodged a claim in mid-2009 on behalf of five elderly Kenyans.
It will be heard on Thursday when four will be present in court. One Kenyan has died since the case was lodged.
Lawyer Dan Leader said about 300 of the 2,000 boxes related to Kenya, and about 30 of those were relevant to the Mau Mau case.
They had been examining them, with historians, since the Foreign Office provided them about a month ago, he said.
Foreign Office minister Lord Howell told the House of Lords: "As a result of searches in connection with a legal case brought by Kenyan Mau Mau veterans against the Foreign and Commonwealth Office, the FCO has decided to regularise the position of the 2,000 boxes of files it currently holds.
"The intention is to make as much of this material as possible available to the wider public."
He said the process of transferring the documents to the National Archives "may take some years to complete".
The four Kenyans - three men and one woman aged in their 70s and 80s - are the lead claimants in the reparations case.
They want the UK government to acknowledge responsibility for atrocities committed by local guards in camps administered by the British in the pre-independence era.
The UK says the claim is not valid because of the amount of time since the abuses were alleged to have happened, and that any liability rested with the Kenyan authorities after independence in 1963.
The armed movement began in central Kenya during the 1950s with the aim of getting back land seized by British colonial authorities.
Historians say the Mau Mau movement helped Kenya achieve independence. But their actions have also been blamed for crimes against white farmers and bloody clashes with British forces throughout the 1950s.
Veterans say they suffered barbaric treatment, including torture, as the British suppressed the rebellion.
The Kenya Human Rights Commission has said 90,000 Kenyans were executed, tortured or maimed during the crackdown, and 160,000 were detained in appalling conditions.
Lord Howell said that "domestic records of colonial administrations" did not form part of British official records and they were kept by the individual states created at independence.
"It was however the general practice for the colonial administration to transfer to the United Kingdom, in accordance with Colonial Office instructions, shortly before independence, selected documents held by the governor which were not appropriate to hand on to the successor government."
The Foreign Office holds about 8,800 files from 37 former British Administrations, including Aden, Brunei, Cyprus, Fiji, Gambia, Jamaica, Kenya, Malaya, Malta, Mauritius, Nigeria, Northern Rhodesia, Palestine, Sarawak, Seychelles, Sierra Leone, Singapore, Solomon Islands, Swaziland, and Uganda.