LONDON: The full extent of the destruction of Britain’s colonial government records during the retreat from empire is disclosed on Friday with the declassification of a small part of the Foreign Office’s vast secret archive.

Fifty-year-old documents that have been transferred to the National Archive show that bonfires were built behind diplomatic missions across the globe as the purge — codenamed Operation Legacy — accompanied the handover of each colony.

The declassified documents include copies of an instruction issued in 1961 by Iain Macleod, colonial secretary, that post-independence governments should not be handed any material that “might embarrass (the) government ... police, military forces, public servants or others e.g. police informers”, that might betray intelligence sources, or that might “be used unethically by ministers in the successor government”.

In Northern Rhodesia, officials were issued with further orders to destroy “all papers which are likely to be interpreted, either reasonably or by malice, as indicating racial prejudice or religious bias”.

Evidence of the purge had to be erased. Documents “should be reduced to ash and the ashes broken up”, while any dumped at sea must be “packed in weighted crates and dumped in very deep and current-free water”. Also among the documents declassified today are “destruction certificates” sent to London by officials as proof they were performing their duties, and memoranda that showed some were struggling to complete their huge task.

A confusing classification system was introduced, in addition to secret/top secret, to protect papers that were to be destroyed or shipped to the UK. Officials were often refused security clearance on the grounds of ethnicity. Documents marked “Guard”, for example, could be disclosed to non-British officials from the “Old Commonwealth” — Australia, New Zealand, South Africa or Canada.

Those classified as “Watch” were to be removed or destroyed. Steps were taken to ensure post-colonial governments would not learn that such files had ever existed. “DG”, said to be an abbreviation of deputy governor, was a code word to indicate that papers were for “British officers of European descent only”.

As colonies passed into a transitional phase before full independence, with British civil servants working for local ministers, a parallel series of “Personal” files could be seen only by governors and their British aides, a system that appears to have been employed in every territory from which the UK withdrew after 1961.

While thousands of files were returned to London during decolonisation, it is now clear that countless documents were destroyed. “Emphasis is placed upon destruction,” officials in Kenya were told.

Officials in Aden were told to start burning in 1966 — 12 months before British withdrawal. “The sifting of documents is a considerable task and you may like to start thinking about it now.” As in many colonies, a three-man committee decided what would be removed to London. The paucity of Aden documentation may suggest that the committee decided that most files should be destroyed.

In Belize, officials told London in 1962 that an MI5 officer had decided that all sensitive files should be destroyed: “In this he was assisted by the Royal Navy and several gallons of petrol.”

In British Guiana, a shortage of “British officers of European descent” resulted in the “hot and heavy” task falling to two secretaries, using a fire in an oil drum in the grounds of Government House. Eventually the army agreed to lend a hand.

The declassified papers show officials asking for further advice about what should not be destroyed. In 1963, an official in Malta asked London for advice about which files should be “spirited away out of the country”, and warned that while some could be handed over: “There may again be others which could be given to them if they were doctored first.”

Not all sensitive documents were destroyed. Large amounts were transferred to Foreign Office archives. Colonial officials were told that crates sent back to the UK by sea could be entrusted only to “a British ship’s master on a British ship”.

Robert Turner, in North Borneo, wrote to the Colonial Office in 1963 weeks before independence, saying his subordinate’s reports — “which would be unsuitable for the eyes of local ministers” — would be sent to London “on the grounds that some at least of their contents may come in handy when some future Gibbon is doing research work for his ‘Decline and Fall of the British Empire’.”

Papers returned to London were not open to historians, however. The documents made available on Friday at the National Archives at Kew, London, are from a cache of 8,800 of colonial-era files that the Foreign Office held for decades, in breach of the 30-years rule of the Public Records Acts and beyond the Freedom of Information Act behind barbed-wire at Hanslope Park, Buckinghamshire, a facility it operates along with MI6 and MI5 (British intelligence services).

The Foreign Office was forced to admit to the existence of the hidden files during high court proceedings brought by a group of elderly Kenyans who were suing the government over mistreatment they suffered while imprisoned during the 1950s Mau Mau insurgency. Even then, the Foreign Office failed to acknowledge that the 8,800 colonial files were just a small part of a secret archive of 1.2m files called the Special Collections held at Hanslope Park.

The Foreign Office is understood to have presented a plan to the National Archive this month for the transfer of the Special Collections into the public domain. Yesterday it declined to disclose details.

The files show that destroying papers pre-dated Macleod’s 1961 instructions. A British official in Malaya reported that in 1957, for example, “five lorry loads of papers ... were driven to the naval base at Singapore, and destroyed ... discreetly”.

A few years later, officials in Kenya were told: not to follow this example: “It is better for too much, rather than too little, to be sent home — the wholesale destruction, as in Malaya, should not be repeated.”

By arrangement with the Guardian