18 May 2011
Last updated at 07:08
The first Olympic torch relay was organised by the Nazis for the 1936 Olympic Games in Berlin. The regime used fire to connect symbolically the Third Reich with ancient Greece, which saw light as a emblem of purity.
After the Second World War, the concept of an Olympic torch relay was reprised for the 1948 Games in London. During what was known as the 'relay of peace', the Olympic flame was carried by an Italian marksman through the streets of Bari on its way to London.
The purpose of the relay is to deliver the Olympic flame to a cauldron at the Olympic stadium, where it burns for the duration of the Games. At the 1956 Olympics in Melbourne, Australian runner Ron Clarke was chosen to light the cauldron at the opening ceremony.
Yoshinori Sakai, nicknamed the 'Hiroshima baby', was born in the city on the day the atomic bomb was dropped. He was chosen to light the cauldron at the 1964 Tokyo Olympic Games.
The Olympic flame is traditionally lit at the original site of the Games - the ancient sanctuary of Olympia in Greece. A parabolic mirror is used to produce a flame from the Sun's rays but if it is not sunny on the day, a flame is used from one of the rehearsals that take place ahead of the official ceremony.
In 1968, the organisers of the Mexico City Olympics produced a whisk-like torch for the "relay to the New World". Shortly after this picture was taken, both athletes were injured when the torch exploded.
The first torch relay for the Winter Olympics took place in 1952 for the Oslo Games. At the opening ceremony for the 1994 Lillehammer Games, ski jumper Stein Gruben leapt into the arena to deliver the flame. Ole Gunnar Fidjestøl was originally chosen to perform the stunt but was injured in a practice effort.
At the Barcelona Games in 1992, archer Antonio Rebollo was asked to light the Olympic cauldron by shooting a flaming arrow towards the cauldron. However, doubts remain over whether it was the arrow that ignited the flame or if it was done by remote control.
The 'Down Under' relay of 2000 started at the sacred site of Uluru (Ayer's Rock) and culminated in Sydney, where one million spectators thronged to line the relay route.
More often than thought, the Olympic flame is accidentally extinguished. Luckily, organisers carry a back-up flame kept in Olympic lanterns. Here, the lantern passes through Wichita, Kansas at sunrise during the 2002 Salt Lake City relay.
In 2006, the torch passed along the St Angelo bridge in Rome, one of 140 Italian cities that the flame visited during the relay, ahead of the Winter Olympics in Turin.
The Olympic torch relay is not without controversy. Ahead of the 2008 Olympics in Beijing, the route of the relay took in many countries and was sometimes lined by pro-Tibetan independence protesters such as these at the Embarcadero in San Francisco.
A day before the 2008 Beijing Olympic Games kicked off, thousands of volunteers gathered on a section of the Great Wall in Badaling, outside Beijing.
Young performers in costume celebrate the last Olympic torch relay - that of the Vancouver Winter Games in 2010. The relay itself was the longest within a single country in Olympic history and featured 12,000 torchbearers.
The torch for the 2012 London Olympics is made from an aluminium alloy and has 8,000 laser-cut circular perforations, one to represent each torchbearer. The torch relay will begin at Land's End on Saturday 19th May 2012 and will last for 70 days.