Secret files from British colonial rule - once thought lost - have been released by the government, one year after they came to light in a High Court challenge to disclose them.
Some of the papers cover controversial episodes: the Mau Mau uprising in Kenya, the evacuation of the Chagos Islands, and the Malayan Emergency.
They also reveal efforts to destroy and reclassify sensitive files.
The Foreign Office says it is now releasing "every paper" it can.
But academics say the Foreign Office's "failure" to deliver the archive for decades has created a "legacy of suspicion".
In particular, the first batch of papers reveal:
- Official fears that Nazis - pretending to catch butterflies - were plotting to invade East Africa in 1938
- Detailed accounts of the policy of seizing livestock from Kenyans suspected of supporting Mau Mau rebels in the 1950s
- Secret plans to deport a Greek Cypriot leader to the Seychelles despite launching talks with him to end a violent rebellion in Cyprus in 1955
- Efforts to deport Chagos islanders from the British Indian Ocean Territories
- Concerns over the "anti-American and anti-white" tendency of Kenyan students sent to study in the US in 1959 - the same year Barack Obama's Kenyan father enrolled at university in Hawaii
In January 2011 - following a High Court case brought by four Kenyans involved in the Mau Mau rebellion - the government was forced to admit that 8,800 files had been secretly sent to Britain from colonies, prior to their independence.
It said the files had been held "irregularly".
Professor David Anderson, an adviser to the Kenyans in the case and professor of African History at Oxford University, said progress had been made retrieving "the 'lost' British Empire archive", but added there was still a "lurking culture of secrecy" within government.
"The British government did lie about this earlier on... this saga was both a colonial conspiracy and a bureaucratic bungle."
He added that the release of the files would help "clear the air on Britain's imperial past".
The 1,200 records being released are the first of six tranches to be made public at the National Archives by November 2013.
They cover the period between the 1930s and 1970s and were physically transferred or "migrated" to the UK.
The archive contains official documents from the former territories of Aden, Anguilla, Bahamas, Basutoland (Lesotho), Bechuanaland (Botswana), British Indian Ocean Territories, Brunei, Cyprus, Kenya, Malaya, Sarawak and the Seychelles.
The archive released on Wednesday details how British colonial officials selected files for secret "migration" back to Britain - using criteria set out in a 1961 memo by the Secretary of State for the Colonies, Iain Macleod.
'Burned and destroyed'
They were instructed to keep papers that might embarrass the UK government, other governments, the police, military forces or public servants; might compromise sources of intelligence; or might be used unethically by ministers of successive governments.
According to Kenyan ministry of defence files from 1961, administrators devised new classifications, such as "Watch", in order to withhold information from indigenous governments.
Files stamped with a "W" could only be viewed by a "British subject of European descent", while "legacy" files could be passed on to subsequent administrations.
Other new classifications included Personal, Delicate Source, and Guard - which could "not be communicated to the Americans".
The Kenyan files also contain references to material being destroyed.
One memo from April 1961 says: "To obviate a too laborious scrutiny of 'dead' files, emphasis is placed on destruction - a vast amount of paper in the Ministry of Defence secret registry and classified archives could be burnt without loss, and I should be surprised if the same does not apply to the CS's (chief secretary's) Office."
Colonial files from the Malayan administration also point to the destruction of papers - ahead of the country's independence in 1957.
In July 1956, an official writing to the private secretary to the British high commissioner questions what to do with archives relating to the Malayan Emergency - the 1948-1960 conflict with communist insurgents.
Referencing the "List C" papers, he writes: "I have been through them and it would seem that some contain items of historical interest in the event of anyone writing a history of the Emergency or biography of former high commissioners.
"The others should be dealt with in detail, but I have not time to do this. Would you agree to their disposal as suggested against individual files in the list?"
An appendix in the same file indicates that "List C" documents are to be "destroyed".
Researchers who have studied the colonial archive say there is little reference to the alleged massacre of 24 unarmed rubber plantation workers by British troops at Batang Kali in December 1948 - during the Malayan Emergency.
Tony Badger, professor of history at Cambridge University - who has been appointed by the Foreign and Commonwealth Office (FCO) to review the files - said the government was releasing "every paper" it could, rather than merely "every paper of interest".
However, he added the release was "long overdue".
"Given the failure of the Foreign Office to acknowledge the existence of - and certainly the failure to manage the migrated archive until very recently, you can amply understand the legacy of suspicion amongst journalists and academics about these records", he said.
He estimated that "well under 1% of material" had so far been held back from release.
A Foreign Office spokesperson said the foreign secretary was "pleased" with the release and "committed" to making the colonial archive "available to the general public as soon as possible".
"These files are an important part of our history and by working with the National Archives we are ensuring that they can be accessed by current and future generations."