Elected as a member of parliament at the age of twenty-four, he was Churchill's parliamentary private secretary from 1926 until 1929. He had been tipped for high office but, eloquent and gifted, his vanity was fatal to his hopes.
In 1929 his friend, Harold MacMillan, lost his seat for Stockton. At the same time he started an affaire with Harold's wife, resulting in the birth of a child in 1930. He was six years younger than Harold, stylish, witty and zestful where Harold was cautious, dull and repressed. Except when his sexual desires were aroused, Boothby hated meanness or betrayal; his staunchness to friends was legendary. Conversely, Harold struck some people as a man who "specialises in disloyalties".

In contrast to Harold's asexuality, Boothby had the sense to be attracted to people who were attracted to him. Though he preferred affaires with women, he had sexual contacts with other men and became a versatile and imaginative lover. The first years of his affaire with Dorothy was overwhelming sexual obsession. Dorothy wanted Boothby badly and he was excited by such a need. Nevertheless their affaire agonised all concerned. Dorothy's conduct was a mixture of public
propriety, private indulgence and that talent for self-deception. Aristocrats had always sanctioned marital infidelity so long as it was discreet. Harold would not jeopardise his political career by giving Dorothy the divorce she craved, and Boothby also shied away as it would bring political ruin for him as well.
In the general election of 1931 Harold MacMillan was re-elected as Conservative M.P. for Stockton and, for this election, was forced to return from his Bavarian sanatorium and speed his recovery from his breakdown. Lady Dorothy campaigned vigorously for him, making public sacrifices to domestic conformity while, at the same time, continuing her affaire with Boothby. Harold needed her support but her continuing affaire confused and hurt him.
For Boothby the affaire was "misery with glorious, but oh so transitory, reprieves," and always living for "next time". In 1935 it was Dorothy's turn to be hurt when, on 21 March, he married her cousin Diana Cavendish, even though two years later they divorced.
In 1940 Churchill told Lord Woolton that "Boothby had much capacity but no virtue", while Harold Nicolson described him as "a fighter with delicate nerves". His political ambitions were wrecked
when he was caught in financial impropriety in 1941. Even in the early 1950s Lady Dorothy still adored him, and on her visits to London would stay not with Harold but at the Dorchester Hotel or occasionally in Boothby's flat.
In 1953 Boothby initiated the long parliamentary struggle for the decriminalisation of homosexual acts which culminated in the Sexual Offences Act of 1967. His robust speeches about sexual prejudice and ridicule of homophobia drew the grubby interest of the "Sunday Mirror", which in 1964 paid him huge damages after implying that he was the lover of the East End gangster, Ronald Kray.
After the Suez crisis Harold became Britain's Prime Minister and Boothby, to Harold's secretary's embarrassment, wrote asking for a Cabinet post and a peerage. Harold's reaction was emphatically, "Of course he must have it", meaning the peerage but not the Cabinet post. In 1958, to the dismay of many, Boothby was gazetted as a Life Peer; but as Harold's star rose, Boothby's fell.

On 21 May 1966 when Lady Dorothy MacMillan died, Boothby was badly affected and drank heavily for a time. He and Harold MacMillan corresponded with some intimacy almost to the end of their lives and met occasionally.

Source: Leo van de Pas