Every time Mark Ellyatt prepares for a record-breaking deep sea dive, he is not the only one who has to take a deep breath.

Half a world away, his mother Joan sits anxiously in her Edgware home and hopes that her son makes it through one of the world's most fascinating, but potentially lethal, sports.

"I get so nervous," she said. "The others always tease me, but he is my youngest, and it's quite dangerous, what he does. On his most recent dive, he had the help of 12 support divers and 30 gas tanks. It took him 12 minutes to get down and six-and-a-half hours to get back up. Divers who come up too quickly can suffer decompression."

On December 19, Mark, of Banstock Road, Edgware, broke the world record for the deepest ever scuba dive going to a depth of 1,026.9ft, which is three-and-a-quarter times the height of Big Ben.

But to spare his mother's nerves, the 34-year-old did not tell her about the attempt until he knew he had succeeded, and come back safely to the surface, off the coast of Phuket in Thailand.

"He never tells me until the dive is done," said Joan. "I never knew that he nearly lost his life when something went wrong with the gas and air mixture on a dive a few years ago. And it took him three months to get over that. But that's our Mark."

Unlike free divers, who hold their breath when they dive, scuba divers use a lot of special equipment and rely on a complex mixture of gas and air to breathe.

Mark had to train for ten years to withstand extraordinary pressures the deeper he dives, which results in the air-containing spaces in his body (such as sinuses, lungs and ears) shrinking to the point where they risk haemorrhaging because the blood leaves them entirely. On his record-breaking dive, Mark had to withstand an increase in pressure of 64lbs per cubic foot of water for every 33 feet he descended. That compares to the pressure of 1lb per cubic foot of air that you might feel standing on a beach.

Mark still counts the house where 73-year-old Joan lives as home, as the rest of his life is spent travelling from one diving destination to another.

"He is an Edgware boy through and through," said Joan. "We are so proud of him, and what he has done."

Born in Edgware, he attended Moat Mount School, now Mill Hill County High School in Worcester Crescent, Mill Hill, and he has always enjoyed swimming.

"He started diving in the gravel pits over here, and those are quite dangerous in themselves," said Joan. "He is the adventurous one."

Mark also holds the world record for the deepest dive to a wreck, which was 557ft, achieved around two years ago off the coast of Guernsey. This has led to the national press assuming that one of Edgware's most daring sons is a Channel Islander.

"For some reason, people often now think he is from Guernsey, or even Jersey, because he lived there for a while, but it would be good if people here could know he's from Edgware.

"He was very determined, and has made something of his life, which is good for an Edgware boy.

"-It's not just a question of putting on your flippers and a mask and off you go."