One man hanging on to a life raft clutched me with a grip of iron when I reached him RAF winchman John Reeson

They had been rescued in a joint effort by passing ships and two helicopters - one RAF and the other civilian.

Rescuers on the Leconfield-based RAF helicopter, which rescued three men, said that by the time they had arrived only one leg of the converted barge was left visible.

Flight Sergeant John Reeson described the horrendous conditions as he had tried to save them.

"We went out through a snowstorm," he said.

"It was clear weather around the oil rig but it was rough. There were waves 15ft to 20ft high. I went down the winch line to men I could see in the water. It was freezing cold. They had been in the water an hour or two before we got there.

"One man hanging on to a life raft clutched me with a grip of iron when I reached him. It was almost impossible to pick him up, but I managed it. He was desperate."

One of the rig workers, Robert Hessey, said the structure collapsed without any warning.

"I saw the crane topple over the deck," he said. "There was a loud sound of grinding and rumbling. I hadn't realised what was happening until I heard someone shouting, 'She's sinking.'"

Last September, after much public anticipation, British Petroleum's rig was the first to discover natural gas in the British sector 42 miles (67km) off the Lincolnshire coast.

Earlier this month Sea Gem also became the first rig to light a flare over the North Sea.

BP said the tragedy will delay its drilling programme. A new purpose-built rig, Sea Quest, is currently under construction in Belfast but it will be some months before it's ready to operate.

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