Boris Johnson is beginning his first day as a Cabinet minister "very excited" to be returning to front-line politics as Theresa May's Foreign Secretary.
His comments came as the Prime Minister prepared to put the finishing touches to her top team.
Mrs May's first night in No 10 saw a flurry of appointments, but the Brexit campaigner's elevation to one of the four Great Offices of State shocked observers.
Speculation had been rife over whether Mr Johnson would be given a role at all, given his spectacular and enforced retreat from the Tory leadership race, days after leading the Leave campaign to EU referendum victory.
His prominent position in that campaign is likely to have played a role in Mrs May's decision as she seeks to reunite the Conservatives.
Chris Grayling had been tipped for the Brexit Secretary job that went to David Davis or the Home Secretary role given to Amber Rudd, and as an ally of Mrs May he is likely to get a job.
The new PM wants more women in the Cabinet and a string of ministers will be hoping for promotion, including Andrea Leadsom, who dropped out of the Tory leadership race on Monday, handing Mrs May the keys to No 10.
Junior ministers who have worked with Mrs May like James Brokenshire could also see an elevation.
All eyes will be on Mr Johnson as he begins his first day as a Cabinet minister, having previously served as London mayor and a shadow business minister between 2004 and 2007.
Speaking after his appointment on Wednesday, Mr Johnson told BBC News: "Obviously very, very humbled, very, very proud to be offered this chance.
"I think Theresa made a wonderful speech this afternoon about her ambitions for the country and how she saw the Conservative government taking Britain forward.
"I completely agree with her sentiments and about opportunity, about giving people better life chances.
"Clearly now we have a massive opportunity in this country to make a great success of our relationship with Europe and with the world and I'm very excited to be asked to play a part in that."
In a flurry of appointments just hours after Mrs May became PM, Philip Hammond became Chancellor and George Osborne left the Government amid claims he was sacked.
Liam Fox was handed a brand new position as International Trade Secretary as Mrs May sought to pull together a team to deliver on the historic vote to leave the EU.
Michael Fallon stayed on as Defence Secretary.
The traditional spectacle of seeing MPs summoned to Downing Street for hiring and firing discussions with the Prime Minister will continue on Thursday amid speculation that Mrs May could reorganise government departments.
Junior ministerial appointments will then follow as Mrs May sets about creating a government driven not by the interests of "the privileged few" but those of voters struggling with the pressures of modern life.
"I know you are working around the clock, I know you are doing your best and I know that sometimes life can be a struggle," she told voters in a speech at Downing Street.
"The government I lead will be driven not by the interests of the privileged few but by yours. We will do everything we can to give you more control over your lives."
Labour leader Jeremy Corbyn welcomed Mrs May's focus on helping the less well-off but repeated his party's calls for her to hold a general election.
He backed promises to give workers a say in boardrooms and act against exploitative zero hours contracts, adding: "But most important is for the new administration to abandon the destructive austerity policies which have damaged our economy and undermined living standards for most people.
"Labour will hold her government to account and make the case for a complete change of economic direction. It is vital that negotiations for Britain's withdrawal from the European Union, in particular, reflect the broadest political agenda."
Liberal Democrat leader Tim Farron attacked the appointment of Mr Johnson, pointing out that during the referendum campaign he compared the ambitions of the EU with Hitler's and "insulted" US president Barack Obama by referring to his "part-Kenyan" ancestry.
"Presumably Boris Johnson's first act as Foreign Secretary will be to apologise to the President of the United States, and then the leaders of our European partners," he said.
"At this incredibly important time that will determine Britain's economic and cultural relations with Europe, it is extraordinary that the new Prime Minister has chosen someone whose career is built on making jokes."