A period of national mourning that was in place since Queen Elizabeth's death will give way to a frantic week of policymaking as Truss looks to address a series of crises.

The former London mayor is still the frontrunner in the race to succeed Theresa May but his lead had been dented by reports of a heated late-night row with his girlfriend.

Boris Johnson, the leading candidate to succeed Theresa May as Britain's prime minister, said on Sunday he would withhold an already agreed 39-billion-pound ($49.6 billion) Brexit payment until the European Union gives Britain better withdrawal terms.