- Actors dressed in ancient Greek costumes light the Olympic torch at original stadium
- Solemn ceremony marks the start of flame's week-long journey to Britain
- Torch will be carried by 8,000 relay runners and cover 8,000 miles across UK
- First runner is Greece's champion swimmer Spyros Gianniotis
Thousands of years after the first athletes competed at the ancient stadium in Greece, a high priestess swathed in white lit a flame from the sun to mark the start of a new Olympiad on Thursday.
The Olympics are as much about tradition and legacy as they are sporting events, with none so vivid as the lighting of the torch which will now wind its way from Olympia to the Games in London.
The solemn ceremony, held in the ruins of the 2,600-year-old Temple of Hera, saw actors in ancient Greek costume use a mirror to harness the sun's rays and light the Olympic torch.
It marks the start of the flame's week-long journey to Britain, where it will begin an 8,000-mile (12,875-kilometer) route across the country before entering at the new stadium in east London.
Taking center stage in the lighting ceremony was Greek actress Ino Menegaki as the traditional high priestess. Among the dignitaries present were International Olympic Committee president Jacques Rogge and London organizing committee chairman Sebastian Coe.
The first relay runner to take the flame was Greece's Liverpool-born open water swimming champion Spyros Gianniotis.
He then passed it to 19-year-old British boxer Alexander Loukos, who grew up in east London where the Olympic Stadium is now situated, but whose father hails from Greece.
Making its way to Britain, the flame will first take in Greek archaeological sites including the Acropolis and Olympic Stadium in Athens, site of the first modern Games in 1896.
Arriving on May 19 at Land's End in the far southwest of England, it will then wind its way through 1,019 communities, carried by 8,000 torch-bearers.
The final leg will run from Hampton Court Palace, the former home of King Henry VIII, before arriving at the opening ceremony on July 27.
The flame will burn until the Games end on August 12 -- a tradition that was revived at the 1936 Berlin Olympics.