Britain's left-wing Labour leader, Jeremy Corbyn, was dismissed by many as a political no-hoper but with the General Election on course for political deadlock he could conceivably become the U.K.'s next prime minister.
While Theresa May, Britain's current premier and leader of the right-wing Conservative party, had been widely expected to win an overall majority, the official results show she has fallen short.
The U.K. could be on the brink of a coalition government for just the fifth time in its political history, with Labour's Corbyn a possible but unlikely candidate for prime minister if the Conservatives fail to agree a deal with another party.
CNBC identifies some of his key pledges.
Corbyn described Trump's decision to back out of the climate pact as both "reckless and dangerous." He also moved to criticize Prime Minister Theresa May of a "dereliction of duty" after she failed to sign a joint statement alongside other EU leaders condemning the U.S. administration.
May expressed her regret with the decision and told Trump in a direct telephone conversation shortly after the announcement that she was "disappointed".
Corbyn has said one of his very first acts as Britain's prime minister would be to call German Chancellor Angela Merkel and French President Emmanuel Macron and reset the tone of Brexit negotiations as well as working to guarantee the rights of EU citizens based in the U.K.
May and Corbyn were both on the same side during the EU referendum in 2016 – against Britain leaving the bloc – although they did not campaign together at any stage.
Corbyn's critics have accused the Labour leader of conducting an insipid campaign for Britain to remain in the EU, especially given his euro-skeptic comments in the past. Corbyn has consistently said he wanted Britain to remain as an EU member.
In short, Labour campaigned against Brexit but now says the EU referendum result must be respected and, while workers' rights is a top priority during formal talks with the bloc, a "close new relationship with the EU" should be targeted.
May and Corbyn frequently clashed over security in the wake of the London Bridge terror attacks at the latter stage of the election campaign.
The Conservative leader accused Corbyn of opposing shoot-to-kill powers and claimed the Labour leader had "boasted" of consistently choosing not to support counter-terrorism legislation as a backbench member or parliament in previous years.
In response, Corbyn urged May to resign given the number of police and firefighters who had lost their jobs in her time as prime minister and Home secretary. He also promised to reverse the cutting of around 20,000 police officers since 2010.
One of the most sensitive British security issues is Trident – the U.K.'s Vanguard fleet of four submarines carrying nuclear missiles.
Corbyn has been a long-standing opponent to nuclear weapons, however, in his party's manifesto; Labour has pledged to renew its support for Trident.
If Corbyn were to enter Downing Street, he has said the U.K. income tax rate would increase to 45 percent for earnings above £80,000 ($103,544) and then to 50 pence in each pound for people with an income of more than £123,000.
Labour has said the amounts raised from extra tax revenues would help the left-wing party fulfill the pledges made in its manifesto.
While, Corbyn has stressed that such tax plans would only impact the top 5 percent of earners, the Conservatives said working families would be forced to "pay the price" for a collection of unfunded spending commitments from Labour.
The Labour leader pledged in the party's manifesto that he would abolish student tuition fees, end zero-hour contracts and bring the railways back into public ownership as franchises expire.
Corbyn's foreword in the manifesto says, "Let's build a fairer Britain where no one is held back. A country where everybody is able to get on in life, to have security at work and at home, to be decently paid for the work they do, and to live their lives with the dignity they deserve."
Watch: Pound gets slammed on UK exit poll results