London 2012 Olympic Cauldron at Museum of London

It was the most closely guarded secret of the London 2012 opening ceremony. Two years on, the Olympic Cauldron is on display at the Museum of London.

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It was an unforgettable moment. Seven young athletes bearing torches jogged towards the centre of the London's Olympic Stadium.

The world caught its first glimpse of the cauldron - a stunning work of art. The athletes touched the edges of the cauldron with their torches, the flame spread and 204 copper petals burned brightly.

The long elegant stems gracefully rose and converged to form a great flame - a symbol the peaceful coming together of 204 nations.

Two years later, as the Commonwealth Games begin in Glasgow, elements of the centrepiece of the London Olympics, designed by Thomas Heatherwick, are on show in the heart of the City of London.

As you walk into the museum's new gallery, the first thing you see is an open section of the torch with 42 of the original steel stems.

You are struck by breathtaking ambition but equally the elegant simplicity of the cauldron.

Image copyright Museum of london

Further into the gallery, 55 stems stand 7m (23ft) upright, wooden moulds for the petals are displayed, while footage from the opening ceremony and the moment the cauldron was unveiled is played.

"It's the moment that the cauldron is lit that is the memorable thing," says Heatherwick. "It was challenging logistically, but that made it I hope more compelling."

However, the apparently seamless moment when the cauldron was lit could have been a complete disaster, he admits.

"To be very honest with you, it never worked, fully, until the actual ceremony," Heatherwick says.

"The most moving moment I've had in my life, was the moment when they started to lift and there was this huge gasp."

The exhibition's curator Georgina Young says the lighting of the cauldron was a "real tipping point" in the public's attitude towards the Games.

Image copyright Martin Rickett/PA

"We noticed a change in sentiment," she says. "The negativity and anxiety before the Games turned into something positive."

"You can see that through people's responses through social media during the ceremony," she adds

"To see it pulled off so seamlessly was a spine tingling moment - it was witnessed by billions and the impression it gave was that London was positive, exciting and working properly."

"It suddenly felt London 2012 was going to be special."

To make the cauldron moment a surprise, its execution was shrouded in a secrecy of Bond-esque proportions.

"The cauldron was tested at 3am and there were no-fly zones over the park," says Ms Young.

Image copyright Museum of london

Former Olympic medallist Sharron Davies, who was also London 2012 ambassador, said: "It was also a complete surprise to so many people.

"A lot of my friends were in on the secret and they were desperately trying not to drop any hints."

Gemma Webster, one of the engineers who built the cauldron, says: "We weren't allowed to tell anybody. I wasn't allowed to go home and tell my family."

"All the drawings, if they weren't used were shredded, everything was top secret," she adds.

Heatherwick says: "It's exciting to reveal the engineering feats that were necessary to make such an extraordinary project happen."

Image copyright Museum of london

With Olympians looking ahead towards Rio 2016, it is hard to imagine how the lighting of London's Olympic Cauldron could be matched.

"The bringing together of many torches was unique to London," says Dr Dave O'Brien, lecturer in cultural policy at City University.

"It will be interesting to see if that influences future designs for the Games."

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