‘Revealed,’ blares the Sunday Telegraph. ‘Churchill’s secret affair and the painting that could have damaged his reputation.’ ‘Winston Churchill’s secret love Doris Castlerosse a blackmail risk,’ agrees The Sunday Times. At least the Daily Mail inserted a note of doubt in its headline – ‘Churchill may have cheated with society’s wildest woman’ – and included a question mark in its opening line: ‘Did Churchill cheat on Clemmie with Cara Delevingne’s great-aunt, who was 1930s society’s wildest and most ecstatically beautiful woman?’

The allegations that Winston Churchill was unfaithful while on holiday in the South of France in the mid-1930s have been knocking around for eighty years, with nothing substantial to back them up besides some pictures that Churchill painted of his alleged lover, the Society beauty Lady Castlerosse, and a photograph of them sitting next to each other on some rocks. However a Channel 4 programme to be broadcast on Sunday night has some new evidence, in the shape of a tape-recorded statement by Sir John ‘Jock’ Colville, Churchill’s private secretary, in which he said that an affair did take place.

Having been researching a biography of Churchill for the past four years, I do not believe it. The Sunday Times states that ‘No historian or biographer listened to the entire tape — until now.’ This is quite untrue; I listened to it many months ago, as has Allen Packwood, the Director of the Churchill Archives, and Colville actually said the words to another historian, Dr Correlli Barnett, back in 1985.When I heard the tape, I decided to investigate the allegation closely – and found that the facts, and other correspondence in the Archive, simply do not support it.

The alleged affair took place in 1933-37, but Colville did not become Churchill’s private secretary until May 1940, so this is at best second-hand information, and Colville does not say that Churchill ever spoke to him about it. He was also speaking half a century afterwards, an absurdly long period of time for historians to take oral evidence seriously.

The fact that Churchill painted his friend Lady Castlerosse – who did have an affair with his son Randolph in the early 1930s – means nothing. He also painted Sir Walter Sickert’s wife Therese, Arthur Balfour’s niece Blanche Dugdale, Sir John Lavery’s wife Hazel, his own sister-in-law Lady Gwendeline Churchill, his secretary Cecily Gemmell, his wife’s cousin Marryot White, and Lady Kitty Somerset. There is no suggestion he was sleeping with any of them. Meanwhile, he painted Clementine three times. ...