It takes two hours of shuddering, noisy helicopter flight from Aberdeen to reach the Sedco Sovereign Explorer, contracted by US company Conoco to drill a well in water 2,500 ft deep. Here, 100 miles north of the Outer Hebrides, is the edge of the Continental Shelf, where the shallower under-sea planes of Europe begin to fall away into the Atlantic's abyss. The depth of water, storms and huge waves also put it on the edge of what is possible for exploiting any oil below the sea bed.
Greenpeace says the oil men should not be here at all. Its first line of argument is that oil and gas reserves sufficient to cause disastrous changes in climate and sea level have already been found around the world, so the hunt for more must stop while efforts to develop non-polluting alternatives must intensify. Its second is that the extreme conditions on the frontier make the risks of a life-damaging spillage too high.
But BP and Shell have already found oil on the frontier and 24 other companies, including Conoco, have government licences to explore and exploit any fields they find. This region is the great hope for the future of Britain's offshore industry; it could keep thousands of jobs and big export revenues far into the next century as North Sea oil and gas runs down.
This summer Greenpeace made its point by occupying Rockall, a tiny isolated rock far out in the Atlantic, for several weeks. Then it attached the survival pod its activists had sheltered in to a BP exploration rig on the frontier for several days. It also obstructed the work of seismic boats which shoot sound waves into the rock strata below the sea bed in a search for potentially oil-bearing formations. And it fought and lost a court case in which it alleged that the Government had failed to comply with EU nature conservation laws when it granted oil companies their frontier licences.
All of this hectic and expensive campaigning in the run-up to the Kyoto Climate Summit next month has had little noticeable effect on the new Government. Tony Blair, the Prime Minister, and John Prescott, his deputy, have explicitly rejected Greenpeace's demand for a halt. Undaunted, Greenpeace intends to hand a petition to Downing Street next week for which more than 200,000 signatures have been collected so far, and it claims the support of several dozen MPs.
Conoco, owned by the huge US Du Pont chemical group, spent thousands of pounds flying a small group of London-based journalists up to Aberdeen and then to the Sovereign Explorer last Friday, to show them how seriously it took environmental concerns. But one thing the company refused to discuss was whether the rig had found any trace of oil. The 90 crew have been forbidden to comment for reasons of commercial confidentiality.
A lubricating mixture of chemicals and water known as drilling mud is constantly circulated down the hole as the drill bit screws into the earth. The mud comes back to the surface carrying rock cuttings which are then filtered out and dumped into the sea, along with some of the mud clinging to them. These liquids used to contain toxic oils, but they are now water- based and far less harmful to life, says Conoco. Besides, by the time they reach the sea bed half a mile below they are very thinly dispersed.
Two vessels are constantly on station near the floating rig, one a support ship for emergencies and the other for any oil spillages. For much of the time, however, the sea is too choppy to put down floating booms to contain the oil which, in calm conditions could then be sucked up. The vessel carries chemical dispersants to break up any spilt oil, but these would probably only be used for a big spill that had some chance of reaching the coast. For small spills, the best environmental option is thought to be letting them disperse naturally.
Conoco says it has searched for Lophelia, the deep, cold water coral found along the Atlantic frontier which Greenpeace says is at risk from oil exploitation, and on which it based its court case. So far, using side-scan sonar and remote-control submarines with cameras and bright lights, the company has found none of the coral around the Sovereign Explorer. But the television pictures reveal plenty of other life swimming and crawling along the muddy, sunless seabed, including a five-ft shark. Dolphins and pilot whales have been seen from the rig at the surface.
As for the dangers of extreme wind and wave, the rig has encountered two gales with wind of more than 70 mph since arriving on station in August. It heaved up and down 30 feet but stayed in place, thanks to eight 12- tonne anchors attached to one and a half miles of chain and cable.
Ian Blood, Conoco's UK head of exploration, accepts that the increasing use of oil and gas was likely to alter climate and that alternatives had to be developed. "They will take their place in the market eventually, 20 to 30 years out," he said. In the meantime, it was up to voters and politicians to decide if they wanted the very significant changes in lifestyles and abandoning fossil fuels involved, he said. "It's not for a company like us to tell the public what to do."