The world's biggest annual sporting event gets under way with a spectacular opening ceremony in Trafalgar Square on Friday evening - the biggest sporting test for the capital in advance of the 2012 Olympics.
The prologue time trial takes place around Westminster, Hyde Park and Buckingham Palace on Saturday and will determine the first wearer of the race leader's yellow jersey. On Sunday the 189 cyclists depart for the first stage proper, a 126-mile route through Greenwich and into Kent.
It has cost £6.8 million to bring the Tour to the capital, but the Mayor expects a £115 million boost to tourism in return.
There will be extra police patrols in the wake of last week's attempted car bombings but this is not in response to any specific threat even though Saturday is also the second anniversary of the 7 July attacks.
Eighteen giant TV screens will be erected around the prologue route to allow spectators to follow the riders, who will set off one at a time from 3pm and will reach speeds of up to 44mph - fast enough to trigger speed cameras - as they hurtle around the five-mile course.
On Sunday the riders leave the Mall at 10.25am, cross a number of bridges and parade past the London Eye and St Paul's Cathedral before heading for Greenwich via Tower Bridge. The race proper starts opposite the Maritime Museum at 11am as the cyclists set off for Canterbury.
Before each stage the tour "caravan" - a procession of 200 sponsors' vehicles dispensing free gifts - drives the length of the route.
Hyde Park will be home to the "people's village" - a free event with interactive cycling displays and French food and drink stalls. This will be open from 4pm Friday until 6pm on Sunday.
Sunday will also see a cycling festival around the prologue route and mountain bike stunts beside St Paul's. Every day that the Tour is in town there will also be "bicycle ballet" outside the National Theatre.
Ken Livingstone said the Tour would provide London with an "unforgettable weekend". He added: "We want the excitement of the Tour de France to encourage even more people to take up cycling."
The race requires substantial road closures and diversions to bus routes from tomorrow lunchtime. Commuters are urged to avoid Trafalgar Square on Friday evening, when the teams will be presented from 6pm.
Engineering work on the Tube in central London has been cancelled for the weekend and 11,000 extra bike parking spaces are being provided. All roads are expected to re-open by 2pm on Sunday.
Transport for London's head of special projects, Mick Hickford, said: "Staging the Tour de France is a huge logistical operation. But this event has been years in the planning and I am confident disruption will be kept to a minimum."
The cyclists, grouped into 21 teams of nine, will also pass through Belgium and Spain before reaching Paris on 29 July after riding 2,206 miles in 21 stages.
The Tour first came to the UK in 1974 when a stage visited Plymouth. Twenty years later it travelled to Brighton and Portsmouth.
www.tourdefrancelondon.com
Riders to look out for
Bradley Wiggins, 27, English Team: Cofidis
Londoners will be pinning their hopes on Bradley Wiggins, an Olympic champion who has a real chance of winning the prologue. Last year Wiggins, who grew up in Maida Vale, came 16th in the opening time trial. He said: "I can't wait to see London turned into a huge cycling stadium."
David Millar, 30, Scottish Team: Saunier Duval-Prodir
David Millar still has much to prove after being suspended from the sport for two years for admitting using performance-enhancing drugs in 2004. The time-trial specialist displayed promise early in his career, winning the Tour prologue in 2000. Shortly after returning from his ban last year, Millar won the 4,000 metres individual pursuit at the British championships.
Fabian Cancellara, 26, Swiss Team: CSC
The current world time trial champion became only the second Swiss to win the one-day Paris-Roubaix race when he triumphed last year. Cancellara won the 2004 Tour de France prologue ahead of Lance Armstrong, but lost the yellow jersey after the first stage.
David Zabriskie, 28, American Team: CSC
Has recorded stage wins in all three Grand Tour races - the Tour de France, Giro d'Italia and Vuelta a España. In the 2005 Tour he became only the third American to wear the yellow jersey. The current US national time trial champion, Zabriskie's main strength is events such as the prologue.
Viewed as something of an eccentric, he sings before stages.
Alejandro Valverde, 27, Spanish Team: Caisse d'Epargne
The golden boy of Spanish racing has been tipped as a possible winner since taking on Lance Armstrong in a head-to-head in the Alps two years ago. The all-rounder is a particularly strong climber and has performed well in sprint finishes.
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