She became convinced that the then vice president, along with businessmen in the South, had orchestrated the Dallas shooting, with gunman Lee Harvey Oswald – long claimed to have been a lone assassin – merely part of a much larger conspiracy.

Texas-born Mr Johnson, who served as the state’s governor and senator, completed Mr Kennedy’s term and went on to be elected president in his own right.

The tapes were recorded with leading historian Arthur Schlesinger Jnr within months of the assassination on November 22, 1963, and had been sealed in a vault at the Kennedy Library in Boston.