A blackmail plot. A smear. Or was it both.

Like many of the best thrillers the Heath Caper affair involves sex, spies and blackmail, and an array of possible resolutions that are all eminently plausible yet cannot all be true. Or can they? I have something of a personal window into the worlds this story touches.

It is an old story, that has just resurfaced — with a new twist — in a radio documentary and Sunday Times article by the BBC’s security correspondent, Gordon Corera. The allegation at its centre was first published in a 1970s book by Josef Frolik, a defector from the Czech secret service. Frolik claimed that his spy colleagues had, years earlier, prepared a homosexual honeytrap for a rising young Tory politician, Edward Heath, in the form of a personal invitation from a handsome (and sexually versatile) young Czech organist, to visit and play the famous organ of the Church of St James in Prague. But Heath (claimed Frolik) was tipped off by MI5 at the last moment, and cancelled the visit.

Corera, however, has established that Frolik’s alleged source — who was indeed in Czech intelligence, did spend time in London, probably did ‘run’ informers, and is still alive — emphatically denies arranging to ensnare Heath. So where does the story come from? Frolik’s British publisher told Corera he thought Heath-hating elements on the Tory right might have concocted it and insinuated it into Frolik’s book (published, in the event, just after Margaret Thatcher had toppled Heath). After the book’s publication, and when confronted publicly with the allegation, Heath brushed if off; and his former principal private secretary, Lord (Robert) Armstrong, who had discussed the allegation with his master, told Corera that Heath was dismissive of the entrapment story. The finger (suggests Corera) points back toward the Tory right, including a spy turned Thatcherite Tory candidate, George Kennedy Young, and another former spy and close supporter of Margaret Thatcher, Sir Stephen Hastings MP.