What is the investigation into the ‘rule-breaking Christmas party’ in Downing Street?

Boris Johnson apologised for the impression caused by the footage (Christopher Furlong/PA)

Boris Johnson has agreed to an internal investigation into allegations of a Covid-rule-breaking Christmas party in No 10 in the face of mounting anger at Downing Street.

The British prime minister relented and allowed an apology of sorts when video emerged of aides joking about holding such a bash last year despite repeated official denials.