This costly legal dispute is rumbling on long after the deaths of most of the parties involved

When Margaret Thatcher approved the transfer of Earl Mountbatten’s personal papers to a university, she put one important caveat on the loan, stating that they should be “properly available to the public”.

That was in 1985, and yet a legal battle over their accessibility grinds on, long after the deaths of most of the parties at the centre of the row.

It is a dispute whose roots can be traced all the way back to 1965, when Sir Michael Cary, second permanent secretary at the Ministry of Defence, wrote to Mountbatten about the publication of any memoirs.

Mountbatten replied that he had “no intention whatever of writing any form of memoirs or biography” but had formed the Broadlands Archive Trust – named after his country home in Hampshire – “to enable a posthumous biography to be written about me if desired”.

He added that he had told the trustees of “the need to submit any form of biography for security clearance before it is published”. He added: “This will probably go straight to the secretary of the Cabinet of the day and I think will take care of the Official Secrets Acts.”

By 1969 Sir Burke Trend, the Cabinet secretary, agreed with the trust that there would be no release of the material without the agreement of the prime minister and Cabinet secretary.

Mountbatten was assassinated by the IRA in 1979, and in the 1980s, with wartime secrets increasingly coming into the open, Southampton University began making inquiries about a loan of the Mountbatten archive for scholarly research.

The matter was duly put before the prime minister of the day, Margaret Thatcher, in a note from Cabinet secretary Sir Robert Armstrong which suggests a “lesser mortal” might not have been allowed to keep such sensitive material at their home, rather than in the National Archives.

Armstrong wrote that some of the papers – which in total filled 38 filing cabinets at Broadlands – would have to be held back from the public, to which Thatcher replied, in a handwritten margin note: “If they are available to ‘scholars’ that is open to the public.”

Armstrong proposed agreeing the loan of the “greater part” of the archive to the university, to which Thatcher replied: “I should not move anything to Southampton unless it can be properly available to the public. Otherwise agreed. MT.”

A further handwritten note on the same document, signed by then principal private secretary Robin Butler, suggests: “I wonder if Sir Robert Armstrong should ensure that the Royal family have no objection. Subject to that, agree this loan?”

Days later, an official note from Butler states that “none of the papers or correspondence about Lord Mountbatten’s relationship with the Royal family is being transferred to Southampton”.

It took until 1989 for the material to be transferred, by which time Butler was Cabinet secretary. Lord Butler told The Telegraph that “there were documents in the Mountbatten papers which were always going to be held back because they raised sensitive issues relating to the Royal family”.

The status of the archive changed in 2010, when the Mountbatten family decided it wanted to sell it.

Southampton University raised £2.8million to buy the archive in 2010, which included a £2million grant from the publicly-funded National Heritage Memorial Fund, in order for the papers to be saved for the nation.

Included in the sale were Mountbatten’s diaries and letters dating back to 1920 and those of his wife Edwina, which did not appear to have been among the material originally loaned to Southampton.

As the university’s staff ploughed through the documents, which filled 4,500 boxes in total, material came to light which Prof Chris Woolgar, then chief archivist of the Broadlands Archive, regarded as sensitive.

He alerted the Cabinet Office to “many references to the Royal family” in the papers and a 10-year ban on the release of the sensitive material resulted.

Then came the request, in 2017, for access to the material by the author Andrew Lownie, who was writing a biography of the couple. The following year, representatives of the Foreign Office and the royal household carried out a fresh “assessment” of the material, and Mr Lownie’s request was turned down.

He appealed to the information commissioner and in 2019 he won his case, with Southampton University ordered to give him full access to the material, in keeping with the spirit of the Thacher memorandum.

The university, and the Cabinet Office, immediately appealed against the decision, and a case that has so far cost more than £600,000 for the two sides’ legal fees has rumbled on ever since.

‘There were documents in the Mountbatten papers which were always going to be held back’