LONDON (Reuters) - Solving the last remaining riddle of the opening ceremony, seven teenagers were given the honor of lighting the Olympic cauldron in the symbolic start to the 2012 London Games.

Opting for young athletes over one of Britain's sporting greats, the seven lit a single tiny flame within a copper petal on the ground, which triggered the ignition of more than 200 petals. Long stems on the cauldron then rose towards each other to form one flame, described as a flame of unity.

(Editing by Alison Williams)