Cyclists have begun racing across the capital as part of the Prudential RideLondon weekend, in one four separate events designed to appeal to riders of all ages and abilities.
Around 50,000 people are taking part in a mass event that saw many of the capital's roads closed to traffic yesterday.
London mayor Boris Johnson was among thousands of others taking part in a 100-mile road race today.
Rugby World Cup winner Matt Dawson has tweeted a picture of himself alongside Olympic rowing star James Cracknell, saying "Here we go. There's no point competing with this fella."
Today more than 50,000 competitors will take part in a 100-mile road race on a route that starts in the Queen Elizabeth Olympic Park in east London, scene of last year's Games, before taking them into the Surrey countryside.
Rugby World Cup winner Matt Dawson, two-time Olympic rowing champion James Cracknell, former Olympic champion sprint hurdler Sally Gunnell and actor Gary Kemp are among the famous faces taking part.
For the first time since London 2012, cyclists have taken over the capital. This weekend more than 70 thousand people are taking part in RideLondon -- billed as the country's largest ever festival of cycling. The aim -- to get more people in the capital on two wheels. Rags Martel reports.
London Mayor Boris Johnson has been wheeled out throughout the year in promotion of the RideLondon cycling festival.
The regular rider will take part in the 100-mile challenge on Sunday.
"My team has told me I will never make it," Mr Johnson said. "They think I am too clapped out to cycle 100 miles but the more they discourage me, the more determined I am to have a crack."
Riders of all ages and abilities will navigate roads around London and Surrey this weekend as part of the UK's largest festival of cycling.
More than 70,000 are expected to get on their bikes for the events at the Prudential RideLondon festival.
The 100 mile London-Surrey, starting at the Olympic Park and finishing on The Mall, is set to be among the highlights.
Up to 20,000 amateur cyclists, including London Mayor Boris Johnson, will be taking part.
Double Olympic gold medallist Laura Trott spoke to Glen Goodman about this weekend's RideLondon cycling event and her love of the sport.
Transport for London has warned that many roads will be closed this weekend for the RideLondon event. On Saturday, Central London will be affected when the FreeCycle ride takes place between the Tower of London and St James's Park.
On Sunday, the London-Surrey 100 ride will take place between the Olympic Park in Stratford and the Surrey village of Ockley.
Several crossings across the river will be closed on Sunday:
- Blackwall Tunnel / A12 southbound - closed from 0100 to 0900 (A12 northbound from A13 closed from 0500 to approximately 0900 and A13 eastbound and westbound from A12 to Leamouth Road is closed from 0500 to 0900)
- Tower Bridge and Southwark Bridge - closed from 0400 to 1515
- Westminster Bridge, Lambeth Bridge & Vauxhall Bridge closed from 0500 to 1930
- Chelsea Bridge, Albert Bridge & Putney Bridge - closed from 0500 to after 1915
- Chiswick Bridge - closed from 0500 to 1430
- Kingston Bridge - closed from 0500 to 1915
- Hampton Court Bridge - closed from 0500. Open from 1530 northbound and 1900 southbound