Save the world (and pass the fags)

They called themselves the Spartans, and like the ancient Greeks they had great powers of endurance and no shortage of courage. It takes plenty of both to board a derelict oil installation in the middle of the North Sea, then remain there for more than three weeks.

Greenpeace's spectacular squat, the Brent Spar oil storage buoy, bears testimony to the hostility of the North Sea environment. After 20 years in the Brent Field, halfway between Shetland and Norway, it is rusty and battered. Stout metal walkways and railings have been bent by 50ft waves.

Greenpeace was determined to stop Shell towing this redundant 14,500- tonne structure out into the north-east Atlantic to sink it 6,000ft. Yesterday, with Shell back in full command, it looked as if it had failed. But it certainly got the world's attention.

The 18 crew members with whom I shared the final three days of the occupation bore some similarities with another, landbound group of environmental campaigners: the most committed of the anti-road protesters. The 18 looked a little grimy, thanks to the lack of running hot water and the oil, rust and grime inside the Brent Spar. They were the same age as the anti-road campaigners - nearly all in their twenties and early thirties. And the Greenpeace crew shared the same commitment andoutlook: large, wicked organisations are endangering the planet, and they must be exposed and stopped at almost any cost.

There the similarities end. For in carrying out the occupation of the Brent Spar, Greenpeace demonstrated resources and organisational abilities closer in character to those of its adversary, the oil multinational Shell, than to the average protest group.

Consider the parallels. Multinational? The cargo ship chartered to back up the original boarding of the Spar sailed from Hamburg, while replacement crew, journalists and supplies were ferried in by chartered trawlers plying from Shetland. At the end of the squat, activists from eight nations were on board. And, just as within Shell itself, those from north-west European nations predominated.

Resources? Shell's budgets are on a different scale to Greenpeace's, but the international campaigning group none the less spent hundreds of thousands of pounds on the operation. As well as hiring the two vessels, it chartered a small aircraft and a helicopter for photography. It had a freelance video cameraman and stills photographer on board to capture life on the Spar. There was also a small fortune's worth of state-of-the- art portable satellite communications equipment there and two large, new diesel generators.

Organisational abilities? Like Shell, Greenpeace has numerous specialist departments, as well as organisations in individual countries dotted around the globe. Greenpeace Marine Services runs a fleet of four small ships, one of which - the Moby Dick - spent several weeks pottering around the Brent Spar on reconnaissance. Greenpeace Communications in London has excellent facilities for wiring colour photographs and video footage of actions to the world's newspapers and television stations.

All this talent and wealth came together to put Greenpeace people on the Spar for most of a month and keep them in the news until Shell evicted them. Members of this "action team" had volunteered for the hazardous mission, but they were all either full-time employees of the organisation or on paid contracts.

They often called themselves a bunch of dirty hippies - which is what they thought Shell thought of them. True, there were plenty of beards, but no one smoked cannabis and they never touched alcohol - the bottle of whisky I brought on board remained unopened.

Surprisingly for committed environmentalists, half of them smoked like chimneys. This caused some problems for Greenpeace Communications, which has a policy of not releasing any video footage showing an activist holding a cigarette.

And although they had grave concerns about the environmental damage that they said would be caused by the sinking of the Spar, they clearly believed in the great powers of the sea to dilute unpleasant substances. How could it be otherwise when they tossed their faeces in a bucket over the side, then hauled up sea water to wash their dirty dishes?

They were a talented bunch. I heard Tim, a New Zealander of Dutch German parentage, talking five different languages fluently. He is a qualified sailing ship's master and managed to get a second satellite telephone link working by delving deep inside a notebook computer, creating a 1,000 Hertz tone and doing something which involved a certain number of decibels.

Ronan, the sole Frenchman aboard, created tasty and varied dishes from simple ingredients. When the end came, Al Baker, a British climber and builder, clambered up a crane tower to perch some 150ft above the North Sea, remaining out of Shell's hands for another 12 hours.

They looked after each other and their visitors, keeping the living quarters clean, taking it in turns to wash up. Naturally they set up recycling banks, collecting paper, plastic, cans and food waste separately.

The activists' captain was Jon Castle, a slow-speaking Guernseyman with a permanent and slightly foolish grin. He was the oldest of the bunch, and the only one with children, and he was respected and obeyed by the crew. Mr Castle was one of the few who were there for the entire 23 days; most came and went after a week or two. He was constantly on the move around the decks of the buoy, organising and encouraging his team.

''This is a good, old-fashioned Greenpeace crew and it's a good, old- fashioned Greenpeace action,'' he told them as the end drew nigh. ''It's good to see Greenpeace getting back into this sort of thing.''

Mr Castle, a veteran captain of Greenpeace vessels, has little truck with some of the newer currents running within the organisation - "solutions- oriented campaigning", signs of sometimes substituting dialogue with industry and governments for confrontation.

As one descended into the Spar's bowels, the atmosphere became ever more eerie and oppressive - large, echoing spaces, unpleasant smells, pitch darkness and the sound of groaning metal and waves bashing the hull. The buoy once had a crew of 30, but it had been empty for four years.

There was much talk of hiding deep within theSpar and holding out for days or weeks after Shell reclaimed the structure. That looked to be a slightly foolish boast after it took Shell just over 12 hours from boarding to reclaim the Spar. Fortunately, the activists never carried out their threat to descend to the lowest "M" deck, far below the waterline, a cramped place where they would have risked being poisoned by hydrogen sulphide fumes.

The senior management of the owner, Shell UK Exploration and Production, was shocked, embarrassed and angered by the occupation. Partly it was a question of lousy publicity, with very few journalists giving much of Shell's side of the story. But the hurt went deeper than that. The North Sea is their place - a dangerous, unforgiving zone where expensive and astonishing feats of engineering have created huge platforms standing among the waves. On a clear day, you could count more than 30 of them from Brent Spar's helideck, in Shell's Brent field, within a mile or two.

The dangers there are very real: nine men died on the Brent Spar during its 15 years of use - six in a helicopter crash, three from gas poisoning. Largely for this reason, Shell and the other oil companies try to create a high-security, authoritarian regime in the North Sea oil platforms.

Greenpeace came crashing into that zone. In doing so, it seemed to shake off the problems and infighting of recent years, in which budgets and staff have been cut and campaigns reoriented. In its own field, it has re-established itself as a world-class organisation.

Shell won the struggle over Brent Spar, but Greenpeace won the clash of corporate cultures.