THE Olympic cauldron which astonished a TV audience of one billion people around the world was constructed in top secret at a business near York.

Scores of staff at Stage One in Tockwith were involved in making the 16-ton cauldron, made up of 204 copper petals – one for each of the countries taking part in the Games.

The cauldron, which was given the personal approval of Prime Minister David Cameron, was lit at the climax of the opening ceremony in London on Friday night.

As athletes entered the stadium each national group was accompanied by a child carrying a petal, engraved with the country’s name. The petals were taken backstage and attached to stainless steel rods, and later lit by seven young athletes. The petals were then raised into the air to merge into one huge flame.

Simon Wood, Stage One sales director, said employees were sworn to secrecy throughout the project to build the cauldron, even keeping family members in the dark.

To aid with the secrecy, the cauldron was nicknamed Betty – apparently after a dog belonging to a colleague of London-based designer Thomas Heatherwick – while the base was called Frank.

Stage One, which operates around the world creating staging, scenery and effects for events, has previously worked on other Olympics-related projects, including the Athens Olympics opening ceremony and the Winter Olympics in Canada. More recently, it made the Olympic rings which have been installed on London’s Tower Bridge.

But Mr Wood said seeing the cauldron being lit at the opening ceremony of a London-based Olympics had been an especially thrilling moment for him and other staff members, most of whom watched the ceremony on TV at home like everyone else, although director Jim Tinsley and managing director Mark Johnson were in the stadium.

Mr Wood said: “It was somewhat nerve-racking. “All the hydraulics had been tested, but there is always the possibility of something going wrong. It had to go right.

“It was a one-off opportunity to show the world what Britain is capable of.”

He said the firm had won the tender to do the work about a year ago and the petals had all been sent off to London about six weeks ago.