The Olympic Cauldron that wowed the world at the opening ceremony failed on one of its final test runs, its designer revealed.
Danny Boyle's spectacular curtain-raiser climaxed with 204 copper petals moving together to form one symbolic flame.
But Thomas Heatherwick, the inspiration behind the unique cauldron, said one of the stainless steel rods holding the burning metal basins became jammed in a secret run-through the day before.
Heatherwick was unaware that the Cauldron hadn't worked only the day before
He told The Sun: "We had been perfecting it throughout the week.
"At the last test session a pin on which one of the petals pivoted had not been put in right."
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The designer, 42, said his team did not let him know about the glitch, which took place during a series of rehearsals at the Olympic Stadium during the early hours of Thursday morning.
They worked desperately to cure the problem and ensure it was fully operational before Friday night's showpiece.
The "petals" of the Olympic cauldron were part of its "dandelion of fire" eye-catching design
Mr Heatherwick added: "On the night I was watching in silence, staring, not aware of anything around me and gripping the bars in front - 'What's going to happen, what's going to happen?'
"When it worked there was an outpouring of relief."
On the night the 8.5-metres tall cauldron, which was crafted in a workshop in in Harrogate, North Yorkshire, worked perfectly with the separate petals seamlessly coming together in 10 rings to create a dandelion of fire after being lit by seven young athletes.
The designer, from London, said: "It really would have been a head-in-your-hands moment if it had not happened on the night."
The cauldron will be split up at the end of the Games and each piece will be returned to a competing national Olympic committee (NOC).