The race for the leader of the Conservative Party is on as Theresa May exits the position.
May will remain prime minister until a new leader is chosen, likely in late July, but has relinquished control over the direction of Britain's tortuous departure from the European Union.
Brexit is still scheduled for October 31 but while her rivals thrash it out over the leadership, the project remains stalled, with the only divorce plan agreed with Brussels stuck in parliament.
May took office after the shock 2016 referendum vote to leave the EU and has spent the past three years working on a departure plan, delaying Brexit twice to try to get it through.
But she finally acknowledged defeat in a tearful resignation speech last month, the culmination of months of political turmoil that has slowly sapped all her authority.
Eleven Conservative MPs are currently vying to replace her, including former foreign minister Boris Johnson, but some are expected to drop out before Monday's deadline for nominations.
The winner will have only a few months to decide whether to try to salvage May's plan, delay Brexit again -- or sever ties with Britain's closest trading partner with no agreement at all.
The government is under pressure from eurosceptic figurehead Nigel Farage, who has called for a "no deal" option and whose Brexit party topped European polls last month.
His party suffered a setback after narrowly missing out on winning its first parliamentary seat, losing to Labour in a by-election in the eastern city of Peterborough on Thursday.
But despite winning, Labour's vote share fell by 17 percent while the Tories' vote plummeted by 25 percent, highlighting the task facing May's successor.
Polling guru John Curtice told the BBC that the result showed Britain was now in a "different political world".
Conservative frontrunner Johnson warned that his party "must deliver Brexit by October 31 or we risk Brexit Party votes delivering Corbyn to No 10", referring to leftist Labour leader Jeremy Corbyn.
Meanwhile leadership rival Jeremy Hunt warned that there was "no future for our party" until Britain leaves the EU.