"Roger Stone was an adviser to Mr. Trump's election campaign.

In 2013, on the 50th anniversary of Kennedy's death, he released a book which claimed to prove that Lyndon B Johnson, Kennedy's vice-president who became president upon his death, was "not only involved in JFK's assassination, but was in fact the mastermind".

This wasn't a new idea: director Oliver Stone's film JFK, released in 1991, had suggested that Johnson may have been involved in a conspiracy.

Last week, Mr. Stone told far-right conspiracy theorist and radio show host Alex Jones that he had personally urged the President to make the JFK files public.

He added that "a very good White House source", but not the President, had told him the Central Intelligence Agency, and specifically its director Mike Pompeo, had been "lobbying the president furiously not to release these documents".

"Why? Because I believe they show that Oswald was trained, nurtured and put in place by the Central Intelligence Agency. It sheds very bad light on the deep state," Mr Stone said.”