London was given a vision of a car-free city when much of the centre was shut to traffic for Britain's biggest mass cycle ride, London Freewheel.
Organisers estimated that more than 50,000 took part - a turnout described by triple Olympic gold medallist Chris Hoy as "overwhelming".
London Mayor Boris Johnson said the event was a 'fantastic opportunity" as he and Hoy cycled in St James's Park.
Riders congregated at hubs around the capital before setting off on the route, which took in landmarks including Parliament and the Tower of London. The Mall was awash with a sea of neon yellow bibs as people of all ages pedalled past Buckingham Palace.
Hoy said: "It's important as a cyclist to promote the sport, but in general it's an opportunity for people to enjoy these amazing locations without the cars on the road, and see how much fun it is to ride a bike. This was a perfect way to encourage Londoners to get on their bikes." Other Beijing cyclists at Freewheel included Victoria Pendleton, Ed Clancy, Jamie Staff and Shanaze Reade.
Members of the public received tips from British cycling coaches and had the opportunity to test themselves against the GB cycling team in the Sky Sports Sprint Challenge.
Mr Johnson, a keen cyclist, said people did not need to be at Olympic standard to brave London's streets by bicycle.
"You only have to be able to wobble along, like I do. We're here to show the benefits of cycling. At any one time, 50 per cent of the bikes in London have not been used for more than a year. Here's a fantastic opportunity for people to get on their bikes and enjoy it."
He added: "It's a safe, quick and very environmentally friendly and healthy means of transport. You would be crazy to get around any other way."
But some people said they did not always feel safe on a bicycle.
Sara Litchfield, from Enfield, was with her nine-year-old daughter Isobel. She said: "Even coming here the cars were atrocious. People were being so rude and not taking notice of the bikes. Now we're here it's fine and there are no cars, it's really nice."
