British Prime Minister Boris Johnson has apologised after a video clip emerged apparently showing his aides joking about an alleged Christmas party held in Downing Street last December, when the country was under strict COVID-19 restrictions. Johnson and other government ministers had repeatedly denied claims, first reported by the Daily Mirror newspaper a week ago, that Downing Street staff held a party on Dec. 18, 2020, in violation of lockdown rules. But leaked footage obtained by ITV showed former press secretary Allegra Stratton laughing with other Downing Street staffers as she appeared to rehearse answers to questions over a lockdown-busting Christmas party. At the Prime Minister’s Questions in the House of Commons on Wednesday, Johnson said that he understood and shared “the anger up and down the country” at seeing No. 10 staff “seeming to make light of lockdown measures.” He said he was also “furious” to see the clip …