PRESS ASSOCIATION -- The year long final countdown to the start of the London 2012 Olympics has begun.
International Olympic Committee president Jacques Rogge declared himself "a very happy man" after visiting the newly-completed Aquatics Centre as part of the celebrations.
He described the £269 million arena as "a masterpiece" and applauded London 2012 organisers for completing the last of the six main permanent Olympic Park venues 12 months ahead of the opening ceremony.
He praised the work done so far but also warned against complacency.
He said: "London has done a great job. I am confident that London will deliver a great Games.
"The operational readiness is an important factor and that is because of the drive of the people who are delivering the Games. The team around Sebastian Coe (London 2012 chairman) and Paul Deighton (London 2012 chief executive) is really a good team."
Throughout the day the focus of the celebrations were at the Olympic Park where 88% of building work is now complete.
Teenage diver Tom Daley took the first leap from the newly-built Aquatics Centre where he hopes to go for gold in London 2012.
Team GB synchronised swimmers also christened the pool with a routine to a Queen soundtrack while local children also got to do several lengths at the Zaha Hadid-designed pool which has a striking wave-like roof.
After testing out the water, swimmer David Davies, a silver medallist from the 2008 Beijing Olympics and a hot tip for 2012, said: "It is that extra buzz because the thing that gets me is how far the stands go back. It is an amazing setting dropping on to a big stage."