Queen Elizabeth II chats with Lord Louis Mountbatten at the Guards Polo Club in Windsor, in 1975, eight years after the plot to topple Harold Wilson - Getty Images

Lord Mountbatten came dangerously close to leading a cabal of industrialists, generals and tycoons plotting a coup against an elected Labour government, a new book reveals.

The 1968 plot was designed to replace Prime Minister Harold Wilson with a coalition government to bring the country together, during what Mountbatten and the conspirators regarded as a time of national crisis.

According to a new biography of Mountbatten, Prince Charles’s great uncle and mentor, it took the intervention of the Queen to persuade him to cut his ties with the plotters rather than acting against Wilson, his Cabinet and Parliament.

Drawing on contemporary diaries of the period, historian Andrew Lownie reveals for the first time the full extent of Mountbatten’s involvement in the plot.

It came amid growing social upheaval, industrial unrest and economic decline, with demonstrations in central London against the Vietnam war, student occupations and increased trade union militancy leading to a belief among some in the establishment that society was disintegrating.

The industrialist Cecil King, chairman of the publishing giant IPC, began gathering senior figures around him who wanted to act.

He believed Wilson, who had been elected in 1964 and again in 1966, should be replaced by a ‘national government’ led by the likes of the pre-war fascist leader Oswald Mosley or a figure of the stature of Lord Mountbatten, who had overseen the withdrawal of Britain from newly independent India in 1947 and had recently retired as Chief of the Defence Staff.

Hugh Cudlipp, the editorial director of The Daily Mirror, told King in April 1968 that Mountbatten had said to him: “Important people, leaders of industry and others, approach me increasingly saying something must be done. Of course, I agree we can’t go on like this. But I am 67, and I’m a relative of the Queen. This is a job for younger men. Perhaps there should be something like the Emergency Committee I ran in India.”

View photos Louis Mountbatten, Prince Charles and Princess Anne at a special preview of the television series The Life and Times of Lord Mountbatten in 1968, the year of the plot against Wilson's government Credit: Topham Picturepoint More

On May 8 that year Mountbatten hosted King, Cudlipp and Sir Solly Zuckerman, the scientist and senior government advisor, at his Belgravia home in Kinnerton St, to discuss what to do about the Wilson government.

According to Cudlipp, Zuckerman expressed deep reservations about a possible coup, stating “This is rank treachery. All this talk of machine guns at street corners is appalling.”

Mountbatten appeared to some of those present to concur with Zuckerman and wrote of the meeting in his diary that evening: “Dangerous nonsense.”

Furthermore he stated in a letter to King in July 1970 that “my views are unaltered” and repeated Zuckerman’s warning that to remove Wilson was “rank treachery”.

However, the mystery of the aborted plot to remove Labour from power deepened when King later released his diary entry for the May 1968 meeting, which according to Mr Lownie’s book The Mountbattens, “gave a rather different account” of what was said.

King wrote that after Zuckerman left the meeting Mountbatten told him “morale in the armed forces had never been so low” and that the Queen “is desperately worried over the whole situation”.

According to King, Mountbatten “asked if I thought there was anything he should do”.

The book now reveals that in November 1975 Zuckerman - in what appears to be an attempt to set the historical record straight - added a crucial diary note to his own file on the May ‘68 meeting.

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