Why PMs get the push

Boris Johnson's announcement that he is set to resign as prime minister threw the British government into turmoil in July - and saw him join a small group of PMs brought down by scandal. RICHARD TOYE explores what we can learn from the demise of previous premiers

- RICHARD TOYE

Waving goodbye Harold Macmillan waves to well-wishers outside hospital, days after bowing out as prime minister in October 1963

Boris Johnson's fall as prime minister early in July was spectacular. It was forced, not by any formal vote, but instead by the resignation of dozens of ministers and aides following a series of damaging political scandals. Indeed, the number of resignations was so great that, had Johnson not quickly reversed his refusal to step down, the business of government might have ground to a halt. In keeping with Johnson's taboo-breaking career, the cascade of ministerial departures was unprecedented but history shows us that the enforced termination of a premier's occupancy of Downing Street is a much more commonplace occurrence.

Of the 20 men and women who have held the keys to Number 10 since the First World War and the dawn of the era of mass enfranchisement, only six have had their prime ministerial careers cut short as the direct result of losing a general election. There are four main reasons that the others found themselves in that position: personal choice, scandal, national crises, and internal party politics.

End of an era Boris Johnson announces his resignation as leader of the Conservative party on 7 July. He is set to stay on as PM until his replacement is announced later in the summer