UK's Boris Johnson resigns as Prime Minister and who could replace him ?

After days of battling for his job, Johnson was deserted by all but a handful of allies after the latest in a series of scandals broke their willingness to support him.

Bowing to the inevitable as more than 50 ministers quit and lawmakers said he must go, an isolated and powerless Johnson confirmed he would resign on Thursday.

"The process of choosing that new leader should begin now. And today I have appointed a cabinet to serve, as I will until a new leader is in place," Johnson said.

"Of course, it is painful to not to be able to see through so many ideas and projects," he said, speaking at a lectern outside Number 10 Downing Street.

"But as we have seen at Westminster the herd instinct is powerful and when the herd moves, it moves."

Johnson said he was sad to be leaving the best job in the world in the statement watched by his wife Carrie, and added: "Them's the breaks."

Support for Johnson had evaporated during one of the most turbulent 24 hours in recent British political history, with finance minister, Nadhim Zahawi, who was only appointed to his post on Tuesday , calling on his boss to resign.

Zahawi and other cabinet ministers had gone to Downing Street on Wednesday evening , along with a senior representative of those lawmakers not in government, to tell Johnson the game was up.

Initially, Johnson refused to go and seemed set to dig in, sacking Michael Gove - a member of his top ministerial team who was one of the first to tell him he needed to resign - in a bid to reassert his authority.

By Thursday morning as a slew of resignations poured in, it became clear his position was untenable.

Londoners react to news the British Prime Minister resigns

Insurance broker Mike Parton said he didn't see potential replacements in the ruling Conservative party, but would be sad to see him go.

"I think he's made quite a lot of mistakes, but he's done a lot of good things as well," he said.

Banker Georges Allan said Johnson "should have been gone a long time. He's overstayed his welcome by a long, long margin."

Fund manager Rosie McMellin said she thought  "the writing's been on the wall" for a while, despite initially being a fan of the prime minister.

"I think it was getting very desperate. I think we've got to look at our reputation on a global basis as well," she said.

Insurance underwriter Aaron Brown gave a much shorter summation of Johnson's premiership, labelling it "a complete shambles with everything."

The Conservatives will now have to elect a new leader, a process which could take about two months, and Johnson will stay on as PM until the autumn.

Below is a summary of some of those who could be in the frame to replace him:

LIZ TRUSS

The foreign secretary is the darling of the Conservatives' grassroots and has regularly topped polls of party members carried out by the website Conservative Home.

Truss has a carefully cultivated public image and was photographed in a tank last year, evoking a famous 1986 image of Britain's first female prime minister, Margaret Thatcher, who was also captured in such a pose.

The 46-year-old spent the first two years of Johnson's premiership as international trade secretary, championing Brexit, and last year was appointed as Britain's lead negotiator with the European Union.

Truss said on Monday Johnson has her "100% backing" and she urged colleagues to support him.

JEREMY HUNT

The former foreign secretary, 55, finished second to Johnson in the 2019 leadership contest. He would offer a more serious and less controversial style of leadership after the turmoil of Johnson's premiership.

Over the last two years, Hunt has used his experience as a former health secretary to chair the 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". Hunt said he would vote to oust Johnson in a confidence vote last month which Johnson narrowly won.

BEN WALLACE

Defence minister Ben Wallace, 52, has risen in recent months to be the most popular member of the government with Conservative Party members, according to Conservative Home, thanks to his handling of the Ukraine crisis.

A former soldier himself, he served in Northern Ireland, Germany, Cyprus and Central America, and was mentioned in dispatches in 1992.

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 for his department's role in the evacuation of British nationals and allies from Afghanistan last year, and the sending of weapons to Kyiv during the recent war in Ukraine.

RISHI SUNAK

The finance minister was until last year the favourite to succeed Johnson. Sunak was praised for a rescue package for the economy during the coronavirus pandemic, including a jobs retention programme, which prevented mass unemployment, that could cost as much as 410 billion pounds ($514 billion).

But he has faced criticism for not giving enough cost-of-living support to households, his wealthy wife's non-domiciled tax status and a fine he received, along with Johnson, for breaking COVID-19 lockdown rules.

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.

He quit the government on Tuesday saying "the public rightly expect government to be conducted properly, competently and seriously".

NADHIM ZAHAWI

The current education secretary impressed as vaccines minister when Britain had one of the fastest rollouts of COVID-19 jabs in the world.

Zahawi's personal story as a former refugee from Iraq who came to Britain as a child sets him apart from other Conservative contenders.

He went on to co-found polling company YouGov before entering parliament in 2010. He said last week at some stage it would be a "privilege" to be prime minister.

PENNY MORDAUNT

The former defence secretary was sacked by Johnson when he became prime minister after she backed his rival Hunt during the last leadership contest.

Mordaunt was a passionate supporter of leaving the European Union and made national headlines by taking part in now-defunct reality TV diving show.

Currently a junior trade minister, Mordaunt called the lockdown-breaking parties in government "shameful". She said voters wanted to see "professionalism and competence" from the government.

She had previously expressed loyalty to Johnson.

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