Lee Cain and Dominic Cummings, the closest advisers to Boris Johnson during his premiership, are expected to give evidence at the Covid Inquiry on Tuesday.

Mr Cain, the former Downing Street director of communications, is scheduled to speak first after his appearance was pushed back on Monday.

He will be followed by Mr Cummings, a chief adviser during the pandemic, who has become one of the former prime minister’s fiercest critics since leaving Downing Street.

Their appearances come after a series of revelations emerged on Monday as Martin Reynolds, Mr Johnson’s then principal private secretary, was called to give evidence.

The Covid Inquiry was told Number 10 tried to “strong-arm” Mr Johnson’s most senior scientific advisers into taking part in a press conference in the wake of Mr Cummings’s lockdown-busting trip to Barnard Castle.