Sir Keir Starmer has promised to build a "government of service" after becoming the UK's first Labour prime minister since 2010.
Speaking outside 10 Downing Street after his party's landslide election win, he pledged to restore trust in politics and “navigate away to calmer waters”.
And appealing directly to voters who did not back his party, he vowed to put “country first" and govern “unburdened by doctrine”.
He was cheered into the famous street by a crowd of supporters, who were waving Union Jacks, and the flags of Scotland and Wales. The PM and his wife Victoria hugged old friends and colleagues who had lined up to applaud him.
Speaking from the lectern, he cautioned that despite Labour's huge parliamentary majority of 174, his aim of "rebuilding" Britain "will take a while".
Sir Keir, who has formally replaced Tory leader Rishi Sunak after an audience with the King at Buckingham Palace, has started to appoint his new cabinet, before it meets for the first time on Saturday.
A short time earlier, in a farewell speech outside No 10, Mr Sunak apologised to unsuccessful Tory candidates and told the public: “I have heard your anger, your disappointment."
He pledged to remain party leader until formal arrangements for selecting his successor are in place.
It marks a dramatic turnaround in fortunes for Sir Keir's party, which won just 203 seats under his predecessor Jeremy Corbyn in 2019, its worst result in terms of seats since 1935.
Despite increasing its share of the national vote by only around 2%, the party has more than doubled its number of seats to 412, a result just short of the historic 179 majority won by Tony Blair in 1997.
Labour's victory came largely as a result of a dramatic 20-point drop in Tory support, with the party down 250 seats to 121, a historic low.
At 59.7%, turnout was the worst since 2001 and only narrowly ahead of the worst-ever 57.2% recorded in the 1918 election at the end of World War One.
In fact, with just two results yet to declare, Labour has won fewer votes overall - 9.7 million compared with 10.3 million - than at the last election.
Its increased vote share came entirely as a result of a 17-point increase in support in Scotland, where it regained its status as the largest party as the SNP slumped from 48 to just nine seats.
On a good night for smaller parties, the Liberal Democrats won 71 seats, the party's best result in a century, whilst Nigel Farage will become one of five MPs for Reform UK, following a breakthrough night for the fledgling party.
The rain in London cleared for Sir Keir as he returned from Buckingham Palace to make his first speech as PM.
He said a "weariness in the heart of a nation" had developed in recent years, likening a lack of trust in politicians to a “wound”.
He added: "This lack of trust can only be healed by actions not words, I know that".
"But we can make a start today with the simple acknowledgement that public service is a privilege," he added.
Sir Keir's path to No 10 followed a cautious campaign in which Labour made few new policy pledges and managed to largely retain the large polling lead over the Tories it began with when Mr Sunak called the election in May.
This polling lead had remained steady since the disastrous premiership of Liz Truss, who lost her previously safe seat of South West Norfolk.
Despite its resounding overall victory, Labour lost a number of former strongholds to independent candidates campaigning on pro-Gaza platforms.
In one of the biggest shocks of the night, shadow minister Jonathan Ashworth lost his Leicester South seat, which had a majority of more than 22,000.
Shadow culture secretary Thangam Debbonaire lost in Bristol Central to the Greens, who celebrated their most successful election night ever after winning four seats, up from the one they held in the last Parliament.
And shadow health secretary Wes Streeting - one of Labour's most high-profile figures during the campaign - saw his majority in Ilford North slashed from more than 9,000 to just 528.
Mr Corbyn - standing as an independent after Sir Keir blocked him from standing again for the party he once led - was also returned in the North Islington seat he has represented since 1983, defeating Labour's official candidate by 7,247.
Manifesto pledges
Labour fought its campaign on a manifesto centred around boosting the UK's sluggish rate of economic growth in recent years.
It pledged to do this largely through changes to the planning system, and by making the country more attractive to inward investment.
But against a difficult economic backdrop, party figures have admitted they face a challenge amid challenges to the public finances.
The party has also promised to overhaul UK employment law, renationalise nearly all passenger rail and set up a state-owned energy investment and generation company, along with boosting green investment.
