UK PM race between Boris Johnson and Jeremy Hunt to conclude

Britain's prime ministerial race entered its final phase as voting closes on Monday evening for counting to begin before Theresa May's successor is unveiled on Tuesday.

The frontrunner throughout the contest has been former foreign secretary Boris Johnson as the Conservative Party's over 160,000 members up and down the UK filed in their postal votes to decide between him and the current foreign secretary, Jeremy Hunt.

They have until 1700 local time to ensure their ballot papers have been submitted in the election after which the counting process is set to begin, with the party's influential 1922 Committee in charge of the election of the new Tory leader who will take charge at Downing Street.

In terms of timeline, May will carry on as caretaker PM for a few days still as she is set to address her final Prime Minister's Questions session in the House of Commons on Wednesday after which she will head to Buckingham Palace to formally offer her resignation to Queen Elizabeth II.

The 93-year-old monarch will then meet the newly-elected Conservative Party leader and invite him to form a new government. The new PM then traditionally makes a statement on the steps of 10 Downing Street before taking official charge before Parliament's summer recess is set to kick off from Friday until early September.

In one of final major prime ministerial acts, May is chairing the government's emergency Cobra meeting on Monday after a British-flagged tanker was seized by Iran in the Gulf last week.

She will receive updates from ministers and officials on the crisis since the vessel and its crew, including Indian nationals, was seized. It will be one of the first big international issue to address for any new PM as well.

With just hours to go before the vote closes, Johnson used his weekly newspaper column in the 'Daily Telegraph' to compare the Brexit negotiations and meeting the October 31 deadline for Britain to leave the European Union (EU) with the same "can-do spirit" behind putting a man on the moon 50 years ago.

He called for optimism in the approach to resolving the controversial Irish backstop issue, the controversial insurance policy insisted upon by the EU but seen as a means of keeping the UK tied to European rules even after Brexit.

The conundrum had resulted in May losing repeated parliamentary votes over her Brexit agreement, ultimately leading to her forced departure as British prime minister.

"If they could use hand-knitted computer code to make a frictionless re-entry to Earth's atmosphere in 1969, we can solve the problem of frictionless trade at the Northern Irish border," writes Johnson.

"It is time this country recovered some of its can-do spirit. We can come out of the EU on October 31, and yes, we certainly have the technology to do so. What we need now is the will and the drive," he said.

He has come under severe criticism from leading politicians, including former British Prime Minister Tony Blair from the Opposition Labour Party, who warned against the prospect of a chaotic no-deal Brexit something Johnson has refused to rule out on several occasions.

Blair writes in 'The Times' to warn that "crashing out without public endorsement would be a gargantuan risk" and "no one knows with certainty the impact of no-deal".

"It could be merely very difficult or it could be catastrophic," he said.

Meanwhile, senior UK Cabinet members Chancellor Philip Hammond and justice secretary David Gauke have declared their intention to resign if Johnson is the one elected as party leader and Prime Minister, in line with their firm opposition to a no-deal Brexit. A number of other Cabinet members are set to follow suit in the event that Johnson wins race over similar Brexit-related concerns.

Besides the Tory leadership race this week, the new leader of the pro-EU Liberal Democrat party is also set to conclude on Monday.

Liberal Democrat parliamentarians Jo Swinson and Sir Ed Davey are battling it out to succeed Sir Vince Cable as party leader and one of them will be announced as the new leader at the end of the vote.