On the day John F Kennedy died, the CIA was working to kill Fidel Castro with a poisoned pen.

Mr Kennedy was assassinated in Dallas in 1963, but Mr Castro survived a CIA plot to kill him with a lethal ballpoint pen. In the end, the Cuban leader outlasted his American rival by more than five decades.

The machinations against Cuba’s communist leader are revealed in a new batch of declassified documents relating to Mr Kennedy’s assassination. The National Archives has been steadily making thousands of documents available to the public, helping to illuminate both the government’s scramble to investigate the President’s death and the Cold War geopolitics playing out around them.

The poison pen plot is striking for its synchronicity. According to a recently released document, on 22 November 1963, a CIA officer in Paris passed a Cuban asset a pen rigged with a hypodermic syringe.

Half a world away, tragedy was engulfing America.

“The evidence indicates that the meeting was under way at the very moment President Kennedy was shot”, the document says.

But it is clear that the attempt, while eerie in its timing, is far from unique. The 1967 document laying it out, entitled “Report on Plots to Assassinate Fidel Castro”, shows killing Mr Castro was a recurring obsession for the American president.