Files relating to the Troubles in Northern Ireland are among thousands of papers reported as missing after being released to civil servants, it has been reported.
Documents on the Falklands war, British involvement in Palestine, and others relating to historical events such as the Russian revolution, are now classed as “misplaced while on loan to government department,” from the National Archives.
The Guardian has reported that the infamous Zinoviev letter – in which MI6 officers plotted to bring about the downfall of the first Labour government – is among the missing documents.
The Home Office declined to say why it was removed from the archives, how it was lost or whether any copies were made.
An assessment of the Northern Ireland security situation, which had been prepared for government ministers in the early 1970s, is also missing, along with one concerning the activities of the Communist party of Great Britain at the height of the cold war.
Another details the way in which the UK government took control of Russian government funds held in British banks after the revolution in 1917.
The National Archives has said Whitehall departments are strongly encouraged to return all borrowed files promptly, but that they are not under any obligation to do so.
“The National Archives regularly sends lists to government departments of files that they have out on loan,” a spokesperson said.
“If we are notified that a file is missing, we do ask what actions have been done and what action is being taken to find the file.”