WHO, WHAT, WHY?
The Magazine answers...
First stop Almaty, 134 cities to go...
Visiting 135 cities in 20 countries, covering 137,000 kms in 130 days. How does the Olympic flame remain burning, even on a plane?
When the Olympic torch is paraded through London on Sunday, all eyes will be on stars like Dame Kelly Holmes and cricketer Kevin Pietersen.
According to the strict traditions of the Olympic movement, and to mark the ancient rituals of the Games, the flame must be kept alive until the closing ceremony of the Games in Beijing in August.
That's all very well when the cameras are rolling and the torch is in the safe hands of a double gold medallist or a world-class cricketer.
The torch is extinguished for flights and overnight
But the flame burns on in enclosed lanterns
Overnight it is in a hotel room with three members of the 10-strong protection team
But what about the more mundane parts of the journey?
A team of about 10 "flame attendants" is responsible for the 24-hour, safe passage of the flame, which has been ignited by the sun's rays on the ancient site of Olympia in Greece.
The torch, which is fuelled by propane, is used to carry the flame during each day's relays, when runners in the relay city carry it, mostly on foot.
But there are several lanterns which are lit from the same source and they keep the flame alive at night or on aircraft when the torch is extinguished.
For air travel, where open flames are not allowed, the flame burns in the enclosed lanterns, which act like miner's lamps.
The torch, the lanterns and the team of attendants, plus other security, fly in a specially-chartered Air China plane bearing an Olympic flame design.
The lanterns spend each night in a single hotel room with three guards - one of which must be awake at any time.
"Security people try their best to keep the flame safe," says a spokeswoman for the Beijing Organising Committee.
"The flame is always burning, whether on the plane or during the relay or overnight. It's kept in the hotel where the core operation team is staying."
The convoy accompanying the torch while it makes its way through city streets has more than 20 vehicles provided by the relay city and they escort the torch in a set order (a section of which is pictured above).
Most of this journey is on foot, but other modes of transport over the years have included dog sled, horse, canoe and camel.
In London, it will be carried on two boats, a bike, a bus and the Docklands Light Railway.
THE 2008 TORCH
The design of the torch reflects the host country
Beijing's torch (above) is 72cms high, weighs 985 grams and is made of aluminium
It can withstand winds of up to 65 kms per hour and stay alight in rain up to 50mm an hour
The fuel of the torch is propane
For a trip across the Great Barrier Reef before the 2000 Olympic Games, a special torch was designed to burn underwater.
The flame made its first trip in a plane in 1952 and has also travelled on Concorde. The torch, but not the flame, has twice been into space.
The torch itself has been produced to withstand winds of up to 65 kilometres per hour and to stay alight in rain up to 50mm an hour. But should it go out, it is lit from one of the lanterns.
This was needed in 2004 when the flame went out in the Panathinaiko Stadium in Athens at the start of the torch relay.
It also went out in 1976 after the Montreal Olympics had started and an official mistakenly relit it using a cigarette lighter. That was doused and it was relit again using the special lantern flame.
Keeping the flame alive is a tradition that began in Olympia in Greece, where the Ancient Olympic Games took place. Fire had divine associations because it was believed Prometheus had stolen it from the Gods.
TORCH RACES OF OLD
There were no torch relays in ancient Games
But there were flame races in Athens called lampadedromia
These honoured certain gods, including Prometheus
The first competitor to arrive at the altar of the god had the honour of renewing its fire.
A flame burned throughout the Games on the altar of the goddess Hestia, situated in the Prytaneum, the building used for the post-Games banquets.
This fire was lit by the sun's rays and it was used to light other fires of the sanctuary, such as the altars of Zeus - the Games were held in his honour - and Hera.
To honour this, the present Olympic torch relay begins at the Temple of Hera several months before the Games, where it is lit by a woman in ceremonial robes using a mirror and the sun.
WHO, WHAT, WHY?
A regular part of the BBC News Magazine, Who, What, Why? aims to answer some of the questions behind the headlines
This gives the flame a purity that is maintained until it enters the Olympics stadium for the opening ceremony.
The final torchbearer, whose identity is kept secret until the last moment, lights the monumental Olympic cauldron in the stadium, which is kept alight until the closing ceremony.
The Olympic flame was reintroduced to the modern Olympics in Amsterdam in 1928 and the first torch relay was held eight years later in Berlin. It has since come to symbolise the Olympic ideal of harmony between nations.
It became a global event for the Athens Games in 2004, which meant that honouring the tradition of keeping the flame going required more planning.
LONDON TORCH RELAY 6 APRIL
1: Wembley 1030BST
2: Ladbroke Grove 1100
3: British Museum 1220
4: China Town 1230
5: Trafalgar Square 1250
6: Southbank Centre 1330
7: Somerset House 1415
8: St Paul's Cathedral 1430
9: Potter's Fields 1500
10: Whitchapel Road 1530
11: Stratford 1600
12: Canary Wharf 1700
13: North Greenwich 1800
Source: Mayor of London