After nearly three years as Britain's Prime Minister, Boris Johnson has resigned as the leader of the Conservative Party and will soon depart 10 Downing Street and the United Kingdom's top job.
Mr Johnson took over from Theresa May as leader of the Conservative Party and Prime Minister in July 2019 and led the party to a resounding victory in the December 2019 general election, with the biggest Tory majority since Margaret Thatcher in the 1980s.
But his time in office was marred by scandals and his handling of the COVID-19 pandemic, which saw the UK endure the highest death toll in western Europe and Mr Johnson himself end up in intensive care after contracting the virus in April 2020.
Mr Johnson lost the support of many Conservative MPs over revelations he and his staff at 10 Downing Street held a series of parties and social events throughout the pandemic while Britain was under strict lockdown restrictions.
The final straw came when it emerged Mr Johnson was aware of an investigation into predatory behaviour by disgraced MP Chris Pincher but denied knowledge of the alleged incidents, failed to act upon them and even promoted him.
How does the UK appoint a new PM?
Unlike in Australian leadership spills, things don't move super quickly and a replacement for Boris Johnson will take some time to appoint.
Leadership candidates will come forward with the endorsement of at least some of their colleagues and a secret vote will be held among Conservative MPs to whittle down the field.
If only one person puts themselves forward, they become leader with no need for a vote from members.
But if there is a contest, the candidate with the fewest votes is removed and MPs will vote again, and so on, until only two candidates remain.
These two candidates are then put to a postal ballot of the wider Conservative Party membership.
Participants need to have been party members for more than three months.
When Mr Johnson won the leadership, he and Jeremy Hunt were the two left standing after the contest, with Mr Johnson gaining 66 per cent of the Conservative Party members' votes and being elected party leader.
So who are the frontrunners now?
Rishi Sunak — former chancellor of the exchequer
Rishi Sunak capped off a meteoric rise from the backbenches in February 2020 when he was appointed the new chancellor of the exchequer — or treasurer — at the age of 39.
Prior to becoming an MP in 2015, Mr Sunak was a banker and hedge fund manager, and some British media outlets have valued his net worth at 200 million pounds ($379 million), but this could partly be down to his wife Akshata Murthy, who is the daughter of Indian billionaire NR Narayana Murthy, who founded IT company Infosys.
Mr Sunak is seen as a rising star in the Conservative Party and has the slick social media presence to go along with it.
Mr Sunak, who resigned from his ministerial role on Tuesday, saying the British public "rightly expect government to be conducted properly, competently and seriously", was the favourite to succeed Johnson until last year.
He was praised for a COVID-19 economic rescue package, including a costly jobs retention program that averted mass unemployment.
But Mr Sunak later faced criticism for not giving enough cost-of-living support to households.
And revelations about his wealthy wife's non-domiciled tax status and a fine he received, along with Mr Johnson, for breaking COVID lockdown rules have damaged his standing.
His tax-and-spend budget last year put Britain on course for its biggest tax burden since the 1950s, undermining his claims to favour lower taxes.
Liz Truss — Foreign Secretary
A favourite among Conservative Party faithful, Liz Truss has been in the cabinet under three successive prime ministers in a range of positions including environment secretary, trade secretary, the minister for women and is the current Foreign Secretary — the first time a female Conservative has held the role.
She is also known for her patriotism — highlighted by a viral speech she gave at the Tory party conference in 2014 where she described the amount of cheese being imported into the UK as "a disgrace".
Ms Truss has a carefully cultivated public image and was photographed in a tank last year, echoing a famous 1986 photo of Britain's first female prime minister, Margaret Thatcher.
The 46-year-old spent the first two years of Johnson's prime ministership as international trade secretary, championing Brexit, and last year was appointed as Britain's lead negotiator with the European Union.
Ms Truss said on Monday that Mr Johnson had her "100 per cent backing" and she urged colleagues to support him.
She backed Mr Johnson over the partygate affair but was also said to be wooing Conservative backbenchers for support should there be a leadership contest.
Sajid Javid — former health secretary
A former banker, Mr Javid has enjoyed a steady rise within the Conservative ranks since first becoming an MP in 2010.
In 2018, he stepped into the powerful role of home secretary after the Windrush scandal claimed Amber Rudd, and was one of the bookies' favourites to replace Mrs May at Downing Street after she stepped down in 2019, but ultimately came fourth in the leadership contest.
In Mr Johnson's first cabinet after he took over the leadership in July 2019, Mr Javid was made chancellor of the exchequer, only to resign six months later after Mr Johnson and adviser Dominic Cummings gave him an ultimatum to sack his own advisers.
Mr Javid was the first cabinet minister to resign in protest over accusations Mr Johnson misled the public over what he knew about sexual harassment allegations against Mr Pincher.
Jeremy Hunt — former foreign secretary
The former foreign secretary, 55, finished second to Mr Johnson in the 2019 leadership contest.
Analysts believe he would offer a more serious and less controversial style of leadership after the recent turmoil.
Over the last two years, Mr Hunt has used his experience as a former health secretary to chair parliament's health select committee and has not been tarnished by having served in the current government.
Earlier this year, he said his ambition to become prime minister "hasn't completely vanished".
Mr Hunt said he voted to oust Mr Johnson in a confidence vote last month.
Ben Wallace — Defence Secretary
Defence Secretary Ben Wallace, 52, has risen in recent months to be the most popular member of the government with Conservative Party members, according to website Conservative Home, thanks to his handling of the Ukraine crisis.
A former soldier, he was mentioned in dispatches in 1992 for an incident in which the patrol he was commanding captured an Irish Republican Army guerilla unit suspected of trying to carry out a bomb attack on British troops.
He began his political career as a member of Scotland's devolved assembly in May 1999, before being first elected to the Westminster parliament in 2005.
He was security minister from 2016 until taking on his current role three years later, winning plaudits as his department evacuated British nationals and allies from Afghanistan last year, and for sending weapons to Kyiv.
Penny Mordaunt — former defence secretary
The former defence secretary was sacked by Mr Johnson when he became Prime Minister after she endorsed Mr Hunt during the last leadership contest.
Ms Mordaunt was a passionate supporter of leaving the European Union and made national headlines by taking part in a now-defunct reality TV diving show.
Currently a junior trade minister, Ms Mordaunt called the lockdown-breaking parties in government "shameful".
She had previously expressed loyalty to Mr Johnson.
Suella Braverman — Attorney-General
An unexpected candidate to throw their hat in the ring is Attorney-General Suella Braverman, who announced her intention to run for party leader the night before Mr Johnson quit.
A former barrister, Ms Braverman was criticised by some of the country's top lawyers after the government sought to break international law over post-Brexit trade rules in Northern Ireland.
She campaigned to leave the EU and served as a junior minister in the Brexit department under Theresa May, but resigned in protest at the then-prime minister's proposed Brexit deal, saying it did not go far enough in breaking ties with the bloc.
She was mocked in the House of Commons on Thursday by her Labour opposite, Emily Thornberry, who prompted laughter by saying it was an "honour" to be standing across from "the next prime minister".
Nadhim Zahawi — Chancellor of the Exchequer
Nadhim Zahawi served as Chancellor for just two days in the final throes of Mr Johnson's tenure. He's most well-known for overseeing Britain's speedy COVID-19 vaccine rollout as vaccines minister.
Mr Zahawi's personal story as a former refugee from Iraq who came to Britain as a child sets him apart from other contenders.
He co-founded polling company YouGov before entering parliament in 2010. His last job was as education secretary.
Mr Zahawi said last week that it would be a "privilege" to be prime minister at some stage.
