Olympics legend Nadia Comaneci carried the 2012 torch on the roof of the North Greenwich Arena as the flame began a seven-day tour of London that will culminate at the Games opening ceremony.
The perfect 10-scoring Romanian gymnast, who won five gold medals over the 1976 and 1980 Olympics, passed the flame on to British ex-NBA basketball star John Amaechi atop the former Millennium Dome, which will host the artistic and trampoline gymnastics as well as the basketball finals.
The Games organisers hope that with the flame now in the British capital, attention will turn towards the sport and the final countdown to the Olympics -- and away from the security and transport fears that dogged the last week.
The flame spent the night safe in the Tower of London, where the British sovereign's ceremonial jewels are kept, following a dramatic arrival in the city Friday, a week ahead of the opening ceremony on July 27.
It was flown in on a Royal Navy helicopter and lowered to the ground by a marine commando carrying it in a Davy lamp attached to his waist.
The final seven days in London are the last legs of an 8,000-mile (12,800-kilometre) journey around Britain that has taken the flame within an hour's travel time of 95 percent of the British population, taking in famous sports venues, historic sites and places of outstanding natural beauty.
Its 36-mile (58-kilometre) tour Saturday around east London, taking in five of the six Olympic host boroughs, started at the Royal Observatory, Greenwich, the location that set the world's prime meridian.
Natasha Sinha, 15, started the relay at 7:20am, or 0620 Greenwich Mean Time.
Robin Knox-Johnson, the first person to sail solo non-stop around the world, took the torch on a lap of the Cutty Sark, the tea clipper ship which has undergone a £50 million (64 million euro) renovation following a fire in 2007.
Comeneci, who at the Montreal 1976 Games became the first gymnast at the Olympics to get a perfect score of 10, then took the flame at the North Greenwich Arena.
"I'm very happy and honoured to be part of the torch relay," the 50-year-old told BBC television on top of the 20,000-seater indoor arena.
"Everybody's very excited, just six days to the opening ceremony.
"This is an historic place and the Olympics came here three times and that's unique too."
Thousands of spectators were in the streets to witness the relay.
Later footballer Fabrice Muamba, who suffered a heart attack during an FA Cup match in March, will carry the flame at the end of the 64th day of its 8,000-mile (12,800-kilometre) relay around Britain.
He will take it through the east London borough of Waltham Forest, where he lived as a boy after moving to Britain from the Democratic Republic of Congo.
Also on Saturday's line-up is Britain's oldest marathon runner Fauja Singh, aged 101 years old, who will carry the torch through the east London borough of Newham.
British triple jumper Phillips Idowu, the Beijing 2008 silver medallist, and rapper Dizzee Rascal will also carry the torch.
Royal Marine Martyn Williams had the honour of bringing the Olympic flame to the host city, abseiling from a Sea King helicopter hovering over the entrance to the Tower of London.
"I obviously checked out the view on the way in and saw London and everybody down here and you think, 'wow this is a bit more than just a normal abseil'," he told AFP.
"But as soon as I got in the door and got my hands on the rope, it is just another abseil from a helicopter so I just had to come down as per usual.
"I said I'd like to do it and the job came to me so I'm very lucky and very proud to be here."© ANP/AFP