LONDON — Four of British Prime Minister Boris Johnson’s most senior aides quit on 3 February, as the fallout of a probe into lockdown parties continues to reverberate at the top of the British government.

Johnson’s chief of staff, head of communications, personal private secretary and long-serving policy chief all quit, the government said, upending the prime minister’s Downing Street operation. The resignations come as the police continue to investigate 12 gatherings that took place in government offices during several Covid-19 lockdowns over the past two years.