Clarissa Eden’s 21st-century counterpart is Sir Philip May. They both married short-term prime ministers who failed in crises because of misjudgements that stemmed from their characters. Both Anthony Eden and Theresa May were hypersensitive to criticism but impervious to other people’s feelings. Eden had explosive bursts of temper while May seethed with tetchy exasperation. Both had politically inexperienced spouses who tendered poor advice while striving to support and protect them. Clarissa Eden, of course, was altogether more distinctive than dull Sir Philip is: a striking beauty of noble ancestry, a steely self-educator, an independent and trenchant career woman, an intellectual and a figure of glamorous fortitude.

Clarissa was born in 1920 with the surname Spencer-Churchill. She is usually described as the niece of Winston Churchill; indeed, the Security Service investigated stories that the Cambridge spy Guy Burgess had been instructed in the 1940s by Moscow to befriend her, seduce her and even marry her because she was the prime minister’s niece. Hugo Vickers, in this lissom, festive and very endearing biography, reveals that she was not genetically a Churchill at all. Indeed, Clarissa is a conspicuously anti-Churchill book. The great war leader emerges as unpardonably selfish and callous; his son, Randolph, comes across as odious; his grandson Winston is presented as a cheat; his daughters are depicted as show-offs or bores and their cousins at Blenheim as dreadful.

Her ostensible father, a stockbroker called Jack Spencer-Churchill, was a Churchill only in name. He was more likely the product of Lady Randolph Churchill’s affair with Evelyn Boscawen, seventh Viscount Falmouth. As Clarissa knew from girlhood, Jack Spencer-Churchill was not her father. Her actual father was Harold (‘Bluetooth’) Baker, a