The Olympic flame was lit in Olympia in Greece today, signalling the final countdown to the start of this year's summer Games in London.

The ceremony, which included actors in ancient Greek costume, took place in the ruins of the 2,600-year-old Temple of Hera.

Using a concave mirror to harness the sun's rays, the flame was kindled on the torch for a relay that will take it around Greece and the UK.

Dignitaries at the ceremony included International Olympic Committee president Jacques Rogge, as well as the head of the London organising committee, Sebastian Coe.

"We promise to protect the flame, to cherish its traditions and stage an uplifting torch relay of which we can be proud," Mr Coe said in a speech.

He said the event would "lift the spirits and hopes of people across Britain and across the world".

After thanks to the god Apollo "king of the sun and the idea of light", the flame was handed to the first relay runner, Greece's Liverpool-born open water swimming champion Spyros Gianniotis.

He then passed it to 19-year-old British boxer Alexander Loukos.

Mr Loukos' father hails from the Greek island of Lesbos and grew up in the east London borough where the Olympic Stadium is situated.

The ceremony marks the start of a week-long torch relay.

The journey will take it to five major Greek archaeological sites, before it arrives at the old Olympic stadium in Athens, which was the site of the first modern Games in 1896.

The last flame-bearers in Greece will be weight-lifter Pyrros Dimas and Chinese gymnast Li Ning, who lit the cauldron at the last Olympics in Beijing in 2008.

A British delegation will receive the flame at a night-time ceremony on 17 May.

In mainland Britain, a soldier wounded in Afghanistan and a 100-year-old woman are among 7,300 people who will carry the torch.

Also among the torchbearers is Jim Redmond, the father of former British 400 metres runner Derek Redmond, who famously helped his injured son hobble across the line during the 1992 Barcelona Olympics.

The London Olympic Games torch will visit the Republic of Ireland before it arrives at the Olympic Stadium in east London on 27 July.

The torch is a reminder of the ancient Olympics, when a flame burned throughout the Games. The tradition was revived in 1936 for the Olympics in Berlin.