Stone-cold sober, probably male, aged over 40 and dressed in layer upon layer of protective clothing, the oil commuters of the North Sea set off to tap Britain's dwindling crude reserves.

While the rest of us are downing coffee and toast, the men and handful of women of the rigs follow draconian safety drills, wriggle into survival suits and climb on board helicopters to begin work in the high risk, high reward environment of the British offshore oil sector.

Since the oil wealth began to flow in the 1970s, the regular commute out to sea and weeks living in the ship-like atmosphere of an oil platform has become a way of life.

"I always think it's very normal. People just going about their business," said Bob Coull, who spent 18 years offshore, working for ExxonMobil.

With an aging North Sea field and an aging workforce, not to mention the constant flow of criticism from environmental campaigners, many argue that the offshore life is drawing to an end. Around half of the reserves of the North Sea have already been tapped and the rest is more difficult and expensive to extract.

But representatives of the oil industry say all the predictions so far have been too pessimistic, that safety and environmental standards are as strict in the North Sea as anywhere in the world and that alternative energy sources are not yet able to replace oil and gas.

Some 195 miles out to sea, the first concrete platform, the Beryl Alpha, was given a life expectancy of 20 years when it was installed by Mobil, now part of ExxonMobil, on the Beryl oilfield in 1975.

More than a quarter of a century on, there is no sign of it being decommissioned and the addition last year of facilities to process gas from the nearby Skene gas field has given it a new lease of life.

At its peak in 1984, Beryl Alpha was producing some 120,000 barrels per day. It is still pumping an average of 90,000 to 100,000 barrels of Beryl - a high quality crude named after the wife of a former Mobil president.

Gas production is around 450 million cubic feet per day, representing nearly five per cent of total British gas demand or the needs of 3.2 million households.

Daily oil production from Beryl would fill a fleet of 630 of the tanker lorries which deliver to petrol stations.

Tom Smith is managing director of Nessco communications, one of the Aberdeen-based oil service companies which in the past has worked under contract on Beryl Alpha and helped to make possible some of the free telephone calls home for the offshore staff.

He argued: "It's more a sunrise than a sunset industry. Every forecast has been wrong and it has been wrong in the right way."

But, as the oil diminishes, he added: "The future does not look like the past. There won't be any more Beryl Alphas."

Equally, the industry hopes fervently that there won't be any more Piper Alphas. The explosion in 1988 on the platform operated by Occidental Petroleum (Caledonia) cost 167 lives, making it the worst accident in the history of the North Sea.

Apart from rigorous safety drills, regulations include a blanket ban on alcohol and any other intoxicating substances which could impair concentration. Anyone caught boarding the helicopter to work smelling of alcohol would be breathalysed. Offshore oil workers watched the World Cup football matches in a state of total sobriety.

If life in the North Sea oil province carries a high price, it also yields a high reward. For an engineer, say, the salary is comparable with across the board engineering rates, but the time off is alluring. After two weeks working on a platform, staff are given around another two weeks off.

From an engineer's perspective, on Beryl Alpha there is the skill of working with the newly added state of the art Skene technology as well as the dense mass of pipes and cylinders of the original structure.

As Mike McAdie, field superintendent on Beryl Alpha, put it: "The challenge is the interface between technology 25 years old and new technology."

When asked about the high point of his 18 years offshore, Bob Coull, who is now back on land working for ExxonMobil's Safety, Health and Environment team, declared: "It's the camaraderie."

Platform manager David Buckland said he feels a loyalty to the Beryl Alpha.

"Beryl has lived through some minor incidents, but she has come through them all well," he added.

On the anecdotal level, some of the most painful incidents have been when the notorious fog, known in Aberdeen as the haar, descends just as two weeks on duty end, making it impossible to board the helicopter home.

To make matters worse, the chocolate biscuits have run out and the satellite television aerial has blown down in a gale. But then every job has its downside.