The centre of the city became a car-free zone for the London Freewheel event, sponsored by Sky Sports, which attracted an estimated 50,000 cyclists.
People congregated at several hubs around London before setting off on the route, which took in landmarks including the Houses of Parliament and the Tower of London.
Pall Mall was awash with a sea of neon yellow bibs as people of all ages pedalled past Buckingham Palace.
Fresh from his triple gold medal success in Beijing, Hoy said the turnout for the event was "overwhelming".
The Edinburgh rider said: "It's important from my perspective as a cyclist to promote the sport, but in general it's an opportunity for people to enjoy these amazing locations without traffic, without the cars on the road, and see how much fun it is to ride a bike.
"It's just fantastic that cycling has started to get a higher profile, and since the Games it's been getting more attention than it has done previously."
Other Beijing cyclists attending the 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 British team in the Sky Sports Sprint Challenge.
Johnson, himself a keen cyclist, said people did not need to be at an Olympic standard to brave London's streets by bicycle.
He said: "You only have to be able to wobble along, that's all, like I do.
"We're here today to show the benefits of cycling for people who haven't used a bike for ages and ages.
"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 and discover what it's all about.
"It's a safe, quick and very, very environmentally friendly and healthy means of transport.
"You would be crazy to get around any other way."
photo Getty Images
photo Getty Images
Courtois, Macgregor, and Östling Advance