It was America's night and thousands of ex-pats living in Britain congregated to watch their country decide who would be their 44th president.
Democrats had been told the polls indicated victory for Obama but that did not stop the nerves jangling.
The US Embassy in London, decked out in stars and stripes, had an eclectic guest list including pop singer Neil Tennant, Conservative David Davis and journalist Janet Street-Porter.
Others settled down to watch the results unfold well into the early hours at Yates' bar in London's Leicester Square.
Party guests were glued to the big screens as Obama edged ahead, capturing the key battleground states of Pennsylvania and Ohio.
It was 0400 GMT before the Democrat candidate broke through the winning threshold of 270 electoral college votes.
There was more good news for the Democrats as they seized Florida, Virginia and Colorado - all of which voted Republican in 2004.
The high drama, late night and jubilant scenes beamed across the Atlantic were too much to handle for some.
They may have voted by post and be far away from home but many will still feel they have participated in an historic election.
Guests called home to talk to friends and family as Barack Obama told thousands of supporters in Chicago: "Change has come to America."
It was the end of the day for America, but the start of a new era. In Britain, it was the end of a very, very long night.