The Olympic Flame will be lit at a ceremony which signals to the world that the countdown to the London 2012 Games has begun.

The ceremony will take place in Olympia, Greece, on Thursday.

A team of the world's top Olympic and sports executives, including International Olympic Committee president Jacques Rogge, Hellenic Olympic Committee president Spyros Capralos and London 2012 chairman Lord Coe, will attend the ceremony.

In front of the ancient ruins of the Temple of Hera, an actress playing the role of a high priestess will light the flame by the rays of the sun in a parabolic mirror.

The flame is placed in an urn and taken to the ancient stadium where Spyros Gianniotis, 32, the world champion 10km swimmer, will be waiting to begin the first leg of the torch relay across Greece.

The Greek swimmer was born in Liverpool to a Greek father and a British mother.

He passes it on to 19-year-old Alex Loukos, who was one of the 30 East End schoolchildren who travelled to Singapore in 2005 as part of the closing presentations for London's bid.

Loukos, a keen boxer, has been training for his role as the second torchbearer by running around the streets near his East Ham home.

The flame will visit Crete, Piraeus, Thessalonica, Xanthi and Larissa, among other places, in a relay around the Greek mainland and islands.

The last torchbearers in Greece will be Chinese gymnast Li Ning, who lit the cauldron at the opening ceremony for the 2008 Beijing Games, and Greek weightlifter Pyrros Dimas.

The flame will be flown to the UK, landing at RNAS Culdrose, near Helston, Cornwall, on May 18 for a 70-day relay.

Starting at Land's End, 8000 torchbearers will carry it to the lighting of the cauldron at the opening ceremony at the Olympic Stadium in Stratford, east London on July 27.

PA