The UK is recognising the historic significance of the US inauguration
Britons have joined in the celebrations to mark the historic inauguration of Barack Obama as US President.
At parties across the UK, thousands of people watched television coverage of Mr Obama being sworn into office.
The viewers included many Americans, who lauded the chance for their country to improve its global relations.
Many Americans attended balls organised by Democrats Abroad in London, Edinburgh, Birmingham, Manchester, Cheltenham, Oxford and Cambridge.
Prime Minister Gordon Brown described President Obama's arrival as a "new chapter in both American history and the world's history".
He praised Mr Obama as a "man of great vision and moral purpose" who would tackle the global financial crisis and other problems such as the environment.
"He's not only the first black American president, but he sets out with the determination to solve the world's problems," he added.
As well as organised events, many Americans joined compatriots in bars to enjoy the spectacle on large screens.
Shanay Norvell, 33, from Atlanta, Georgia, took in proceedings at the Texas Embassy Cantina in London's Trafalgar Square.
"The highlight was [Mr Obama] speaking about all the ways we will change and in making friends with everyone in the world.
"But I also liked the way he said that if anyone is against us, we won't back down."
Fellow American Gillian Bagwell, 49, said: "We're sorry for Bush. It has really been exciting watching how other nations across the rest of world have been following it.
"Finally we have change and it feels good to be American again."
Their mood was shared by those at the UK's inauguration parties, many which involved an element of black culture.
Nia Bellot, 40, took seven-year-old son El-Hajj to watch the event at the Bernie Grant Arts Centre in Tottenham, north London.
"I wanted him to celebrate the day, this historic occasion, it's especially historic for him as a black child," she said.
Bola Ogun, from the Windsor Fellowship, which tries to raise black achievement, said Mr Obama's presidency would remind young people "that hard work, dedication and doing the right things can pay off.
"We see all the negative images of black people within our society and what Barack Obama is going to do is balance that out," he said.
People watched history unfold at live screening parties at the West Indian Centre, Leeds; Queen's University, Belfast; and the Kuumba Imani Millennium Centre in Toxteth, Liverpool.
Americans in the UK threw parties to mark the new president taking office
Singers Kelly Rowland and Mica Paris were performing at a Yes, We Did event at London's Intercontinental Hotel in Park Lane, London. The event recognised black Britons who have made a difference.
Meanwhile, speakers and musicians were appearing at a party held by the Ibbamo Trust - a charity helping people reach their full potential - at the capital's O2 Arena.
However, not all Britons were content to watch via satellite link.
Onjali Bodrul flew from London to see a man whose career she and her friends have followed since she was a political science student at Oxford four years ago.
She said: "He's the first man in politics in a long time we don't hate. It's like a football match, it's so exciting."
Ruth Pitter, 47, and Valerie Mower, 44, from Bristol, were also among those who headed to Washington to share in the moment on US soil.
Ms Pitter said she was hopeful the historical election across the Atlantic would have a global impact.
"I feel this is the time now for my community to really see a change," she said.
Before the inauguration, Ashok Viswanathan, vice president of campaign group Operation Black Vote, said he hoped the event would inspire people from ethnic minorities to enter politics.
With the correct systems in place, he said, the UK could see a black leader of one of the main political parties within the next 10 to 15 years, and a black prime minister within 30.
The Queen had sent a personal message of support to Barack Obama on the eve of his inauguration ceremony.
While her words have not been released, it is understood she sent him best wishes for the swearing-in event and his presidency - the 12th during her reign.