The work of the most widely respected political journalists of the 20th century was subjected to intense scrutiny by ministers and officials because of fears that the machinery of government was being undermined by serial leaking.
Papers show that during 1978 more than 30 articles written by Peter Hennessy of The Times were examined closely by James Callaghan’s government. This prompted Sir Ian Bancroft, head of the Home Civil Service, to impose an embargo on all civil servants having contact with the media without express ministerial authority.
According to a memo written by one of Callaghan’s private secretaries on February 10 of that year, the prime minister had reacted “strongly” to an article that included comments of senior civil servants. Callaghan ordered that immediate action be taken to “re-establish a proper behaviour” among senior Whitehall mandarins.
Undeterred, Mr Hennessy’s sources continued to leak information. On April 24, the Times carried a report by the journalist detailing how a cabinet committee had secretly begun to review the quality and quantity of peacetime intelligence and security information that could be safely revealed under the 30-year rule without jeopardising current operations.
Labour had made an election manifesto commitment in 1974 to replace the Official Secrets Act, only subsequently to decide against a Freedom of Information Act during the Callaghan government.
As part of his response to the Hennessy articles, Callaghan asked each member of the cabinet whether they were satisfied with the professional conduct of their civil servants. A subsequent report to the prime minister noted that every senior minister had expressed satisfaction, with the exception of Tony Benn.
A later note showed that by September 8 Callaghan had decided against risking a public political row by ordering a formal interdepartmental inquiry, opting instead for having his principal private secretary, Kenneth Stowe, “have a word with Sir Howard Smith [the head of MI5] about possible next steps”.
MI5 files from this period remain secret, although all the evidence suggests that Callaghan was advised to let the matter drop and, in contrast to the current Damian Green affair, resisted the option of calling in the police.
Mr Hennessy, today a professor of contemporary British history at Queen Mary college, University of London, was among those examining the papers disclosed under the 30-year rule.