The torch for the London Games will set off on a seven-day journey across Greece before it leaves for Britain on May 18.

"We promise to protect the Flame; to cherish its traditions and to stage an uplifting torch relay of which we can all be proud and which can inspire a generation," Coe said in his brief speech in front of the International Olympic Committee president Jacques Rogge.

"As torchbearers lift the Olympic flame in the days and months ahead, it is our hope that they will also lift the spirits and hopes of people across Britain and across world," said the former Olympic champion.

On a glorious, sunny day in this lush valley of the western Peloponnese, site of the ancient Olympics, actress Ino Menegaki, playing the role of a high priestess, will light the torch using a parabolic mirror to kick off the last straight for the London Games preparations, less than 100 days before the opening ceremony.

First torchbearer Spyros Gianniotis, a Liverpool-born Greek swimmer who won the gold medal in the 10km open water event at the 2011 world championships, will set off after paying tribute to Pierre de Coubertin - founder of the modern Games - whose heart is buried near the ancient site.

He will then pass it to 19-year-old Alexander Loukos, a Briton of Greek origin.

"We will involve young people from all backgrounds, cultures and faith groups in the torch relay, reflecting London's immense diversity and creativity as a global destination and voice for young people," said Coe.

"This is the second time the people of the UK have gathered here to celebrate igniting of the flame," he said.

"In 1948, shortly after the Second World War, my predecessor stood where I am today and made the first tentative steps in turning the world from war to sport."

"We find ourselves in challenging times again and turn to sport once more to connect the world in a global celebration of achievement and inspiration."

London is the only city to have lit the torch twice in Olympia.

The 70-day torch relay will travel 12,800 km around Britain, taking in 1,018 villages and the 1,085-metre summit of Snowdon, before culminating with the lighting of the Olympic cauldron in the Olympic Stadium on the opening day of the Games on July 27.

The relay will also take in landmarks around Britain with the flame travelling by canal boat, cable car, tram, steam train, hot air balloon and even motorcycle sidecar on the Isle of Man TT course. REUTERS