The Foreign Office has pulled dozens of files from the National Archive amid fears that they contain details of British military assistance in India’s crushing of Sikh dissent in the 1980s, The Times has learnt.

Whitehall papers released to the archive this summer were recalled abruptly last month, days after the Sikh Federation wrote to Boris Johnson, the foreign secretary, saying that they had uncovered “delicate information” concerning “UK military assistance to India”.

A researcher working for the federation at the Kew archives found a note referring to the possibility of an SAS involvement after “an Indian request for military assistance in the setting up of a National Guard for internal security duties”.

The note, marked confidential, was written on July 3, 1984, a month