THE WHALE appeared on the starboard side of the boat. It was about 40 yards away, a sleek black back arching for a few seconds on the surface, before disappearing below the water. For Helen, this moment was the culmination of a lifetime's ambition.

'Oh God, yes,' she screamed, in the unrestrained manner other people reserve only for the moment Manchester United score a goal. 'Look. Look. Oh God. Andrew, Andrew, did you get that?'

She turned to her boyfriend, who was emerging, with his bazooka-sized telephoto lens, from the cabin of the boat.

'No,' Andrew confessed. 'I was in the loo. Bloody typical.'

Helen and Andrew, together with seven other cetacean enthusiasts, were taking their summer holiday on a boat, just off the Isle of Mull, watching whales. The couple had driven up from Leicester and paid more than pounds 400 each for five days of undiluted pleasure. And here they were, within an hour of setting out from Mull for the first time, about to commune with the biggest creature in the British Isles.

'Don't worry,' Janine, a member of the boat's crew, said to Andrew. 'He'll be up again in a few minutes. Nine is the longest time we've had to . . .'

'There he is, oh Jesus,' shouted Helen as the whale came up again for air, close enough to the boat for its occupants to appreciate that oral hygiene is not high on a whale's list of priorities: its spout smelt worse than a cat's breath after a tin of pilchard Whiskas.

'Why do you automatically assume,' asked Anthony, a bearded computer programmer from Surrey, politically correctly, 'that it's not a she?'

According to Richard Fairbairns, who was their skipper and host for a week, the party was very lucky: conditions were perfect for spotting whales - grey sky, grey sea. Against this uniform greyness, a whale's black dorsal fin could be seen miles away.

Mr Fairbairns had first encountered whales off Mull four years ago. He had been a farmer in Norfolk and escaped up to the island in the late Seventies. When he found the farming tougher going than in East Anglia, he had started to take tourists on wildlife cruises, spotting birds, catching fish, scoffing cream teas on the Isle of Muck. One day he was in his boat, gently bobbing in the water, lines over the side, when a minke whale appeared and hung around for about an hour, checking him out.

'It was the most extraordinary thing you could imagine,' he said. 'Quite, quite extraordinary.'

Particularly as received wisdom had it there were no whales resident in the area. There used to be; the whalers of Harris were catching blue whales off the Hebrides as recently as the Twenties. But whaling had, it was thought, exhausted stocks in this part of the world long before the worldwide commercial whaling moritorium was instituted in 1988. Yet here was one, sizing up his boat.

After this meeting, Richard Fairbairns became obsessed with the minkes. He saw them more and more and wanted to learn all about them, so he turned his wildlife cruises into whale-watching trips - as much for his own benefit as for the tourists. He has an impressive track record of finding the eight minkes he reckons live in his patch; since May this year, going out practically every day, he has failed to spot whales on only three occasions.

'I've developed a nose for it,' he said. 'I don't know what it is, just a feeling for the conditions, the activity of the seabirds, that sort of thing. I think I know where they are.'

This is not information he is anxious to share, for obvious commercial reasons. There are other operators in the area, keen to get in on his act, who have taken to following his boat.

Rivals are not the only people who have heard of Richard Fairbairns. On board his boat this summer is Vassili Papastravou, a zoologist sponsored by the International Fund for Animal Welfare, who is embarking on a five- year study of the Mull whales.

'Whale research has been taken over by mathematicians, making mathematical models and projections of numbers,' Vassili said, demonstrating an impressive program on the computer which he has installed on the bridge of Richard's boat. 'After the International Whaling Commission meeting finished in Glasgow last week, we took one of the mathematicians out on a trip here. He had been studying minke whales for 10 years, and it was the first time he had seen one in the flesh.'

Vassili and Richard enlisted the nine whale-watchers on this trip as research assistants. They placed them at stations around the upper deck and gave them each a section of sea to scan.

After their early first encounter, it was some time before the team spotted a whale again. Up on deck, peering at the waves for hours on end, the eyes began to fog, mirages began to appear, you felt like a character in Moby Dick. A floating sea bird, a clump of seaweed, even a small wave might just have been a whale's fin.

Peter, a German naturalist, was a veteran of five whale-watching holidays around the world. He had seen killer whales off Vancouver, hump- backed whales off Newfoundland. He had been determined to come to Mull to look for minkes ever since the time, five years ago, when he had seen a whale from the ferry between Eigg and the mainland.

'It was raining and I was the only person on deck,' he remembered. 'I knew it was a whale, but nobody believed me. They thought I was seeing things. I had to come to take pictures to prove I was right.'

The agreed terminology was to shout 'blow' every time a whale broke the water, much as the old whalers used to. But after a few hours on watch this tended to come out as: 'Is that one? Over there? Is it? Oh God. Can you see? There, there, just there. Is that one?'

'No it's a canoeist,' said Janine.

When a whale was finally spotted, to the starboard again, Richard cut the engine, leaving the boat to drift in the water. He didn't chase the whales, he explained. If they went off in the opposite direction, he let them be. It was up to them to come over to the boat, to 'associate' if they so wished.

With the engine off, the water lapping the side, the tension waiting for the whale to surface again was almost unbearable. Nobody spoke. Amanda, a schoolgirl from Jersey, stared intently at the stop-watch she had been given. A large wave hit the back of the boat and everyone span round imagining the whale had arrived on deck, mouth open, Jaws-like. Someone moved and Richard snapped at them to keep still: the whale could hear movement and we didn't want to frighten it off,

did we?

Then there was a loud snort, a shout of 'blow' went up and everyone trained their whirring motor drives on the beast as it surfaced on the other side of the boat. Minkes are quick, taking air for only a few seconds. The Norwegians reckon they can fire a harpoon through the whale's spine as it breaks the water, killing it instantly. They must be tidy shots; most of the whale- watchers didn't even have time to shoot the things with their cameras.

Each 'blow' was communicated by walkie-talkie down to Vassili, who recorded it on his computer. When another whale suddenly broke the water, one of the members of the party became very excited.

'Are we going to do a blow job on this one too?' she asked. 'Oh, I don't think I quite meant that.'

The whales, however, were too busy searching for food to be detained for long by passing boats, and disappeared into the distance. As the watchers returned to point duty, Kenwyn, a store detective from Bexleyheath, and her friend Jenny, a Metropolitan Police sergeant, said that they were delighted to be used as unpaid researchers.

'I want to see everything before we bugger it all up,' said Kenwyn, explaining that she always took an environmental holiday. 'I went on safari last year, I'm climbing Kilimanjaro in September. And to feel that we might, in a very small way, be helping is even better.'

Looking out over the sea, empty except for a couple of diving razorbills, Kenwyn said that as she spent her time nicking people, she needed holidays like this to restore her faith in the world. She was pleased that she was unlikely to see much criminal activity out here.

'I don't know,' joked Jenny. 'We might see some foreign trawler after our fish.'

Anthony was quick to politically correct her. 'They're not actually our fish,' he scolded.

Information on Richard Fairbairns's Sea Life Cruises on 06884 223.

(Photograph omitted)