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 . Comment: First runner is Greece 's champion swimmer Spyros Gianniotis .
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 .