The final rehearsal for the lighting of the flame that will burn at the London Olympics went off without a hitch under bright sunny skies in the birthplace and site of the Ancient Games. Standing in front of the 2,600-year-old Temple, an actress dressed as a high priestess used a concave mirror to focus the sun's rays and light a torch. That flame will serve as a backup in the unlikely event that clouds hide the sun at Thursday's official lighting ceremony. This has happened only once in recent memory for the Summer Olympics — in 2000, ahead of the late-season Sydney Games — but clouds have disrupted three of the previous four Winter Games ceremonies. The rehearsal went on without almost any VIPs and in front of hundreds of visitors to the archaeological site, access to which will be restricted under tight security in Thursday's official ceremony. In a choreographed departure from previous ceremonies, a chorus of 13 young men struck poses from Olympic sports and performed their own ritual dance in tandem with the 17 priestesses. The first two torchbearers are both born in the UK, the sons of Greek fathers and British mothers. Spyros Gianniotis, a 32-year-old Liverpool-born swimmer, who won a silver medal for Greece in the 5-kilometer open water event four years ago in Beijing and who will take part in his fourth Games, will hand over to Alex Loukos, a 19-year-old born and raised in the east London borough of Newham, where the Olympic Park is located. After a 2,900-kilometer journey through Greece using 490 torchbearers, the flame will be handed to London organizers in Athens' Panathenian Stadium, where the first modern Games were staged in 1896, on May 17. In contrast to the two previous Summer Games, where the Olympic flame relay went around the globe, it will leave the UK only once, to pass though Dublin on June 6. The Olympic are from July 27 to Aug. 12.