The documentary has unearthed a 1985 interview with Churchills private secretary, Jock Colville, who revealed that he had an affair with Lady Castlerosse, reported Variety.
"I dont think that in his 60 or 55 years married life he ever slipped up, except on this one occasion when Lady Churchill was not with him and by moonlight in the south of France, . he certainly had an affair, a brief affair with Lady Castlerosse as I think she was called. Doris Castlerosse, yes thats right," Colville said on the tape, excerpts of which are voiced by an actor in the documentary.