Seven years of planning have finally come to a head with the start of the much-anticipated opening ceremony for the London Olympics.
The £27m extravaganza entitled Isles of Wonder is expected to attract a global audience of billions.
It is being staged at the Olympic Park in Stratford where the audience of 62,000 includes the Queen, Prime Minister David Cameron and US First Lady Michelle Obama.
The highlight will be the arrival of the Olympic Torch, which today ended its 8,000-mile journey around the UK at Tower Bridge .
Mystery still surrounds who will be given the honour of lighting the Olympic flame, however.
The Queen, Sir Steve Redgrave, Sir Roger Bannister, Daley Thompson and David Beckham have all been touted as contenders
Ceremony director Danny Boyle has dedicated the spectacular to the 15,000 volunteers who are helping to bring it to life.
"The thing about directors is that they just sit at the back in the end," the Oscar winner said
"This is a live performance and it's the actors, and in our case they're volunteers, who have to get up there and do it."
Before leaving for Stratford, the Queen and Prince Philip held a reception for foreign heads of state and government at Buckingham Palace.
As well as Michelle Obama, the guests included German President Joachim Gauck, French Prime Minister Jean-Marc Ayrault, Italian President Giorgio Napolitano and Russian Prime Minister Dmitry Medvedev.
The transport network was said to be running extremely well as thousands of people travelled to the opening ceremony.
Transport for London (TfL) said that while services were very busy, there were no major delays on the main line and Tube.
Earlier, thousands of people lined the River Thames to cheer the Olympic torch as it made its way across London from Hampton Court.
Bells rang out around the UK to mark the final countdown. Among them was London's Big Ben which chimed non-stop for three minutes from 8.12am.
Mr Cameron said Britain was ready to welcome "the greatest show on Earth", adding: "This is a great moment for our country, so we must seize it."
Mayor of London Boris Johnson told Sky's Adam Boulton the build-up to the Games had been an "amazing thing".
"You're seeing a kind of benign contagion passing from person to person," he said. "... it is a wonderful thing to see."