What will Sue Gray's inquiry mean for UK PM Boris Johnson?

Senior civil servant Sue Gray is carrying out an investigation into alleged Covid rule breaking in Downing Street and government departments.

The purpose of the investigation is to establish "a general understanding of the nature" of gatherings that took place and whether any "individual disciplinary action" should be taken, the inquiry's terms of reference said.

Her report is likely to be a largely factual account of any gatherings, and she cannot rule on whether lockdown laws were broken.