Winston Churchill had a short affair with the dazzling socialite Lady Doris Castlerosse in the 1930s, according to his former private secretary, research has found.

A recording by Churchill’s former private secretary, Jock Colville, in which he disclosed that Britain’s war leader had engaged in a short affair with the society beauty in the south of France, has been revealed by Dr Warren Dockter of Aberystwyth University and Professor Richard Toye, head of history at the University of Exeter.

Colville, a close confidant and trusted aide of Churchill, said in the taped 1985 interview for Churchill College, Cambridge, that the story that he had to tell was rather scandalous and that he did not want it disclosed for a long time to come.

He revealed that when he visited Winston and his wife Clementine in the late 1950s, Churchill’s literary assistant Denis Kelly had presented Clementine with a set of love-letters from Lady Castlerosse. Clementine Churchill, he recounted, read the correspondence and turned pale.

According to Colville, Clementine was anxious about the episode for months and told him she had never previously thought that Winston had been unfaithful to her.

The research, to be published in the journal in the Journal of Contemporary History – and featured in the Channel 4 documentary Secret History – includes testimony from Castlerosse’s niece, Caroline Delevingne, who disclosed that her family had known about the affair.

Documents in the family’s possession include – in addition to photos of Churchill and Lady Castlerosse together – a long and affectionate 1934 letter in which he compared her to a ray of sunshine.

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