TREVOR Blaney and Robert Stuart look like anyone else in the pub. They're wearing jeans and T-shirts, they order pints. Look again: this unemployed Yorkshire mechanic and hippy solicitor could soon be earning as much as pounds 70m a year each.

The brainwave which might revolutionise their lives looks so ordinary that only an alert plumber might recognise a potential gold-mine. It is a bath- plug with an internal mechanism that automatically depresses at a set water pressure, allowing water to escape. If the taps are turned on in a full bath, the plug will keep the water level constant.

This means Muslims, who are required to wash in circulating water, could discover the joys of the bath. It could also slash the annual cost of water damage in England and Wales, estimated at pounds 1.4bn, by stopping baths overflowing ever again.

When Trevor, 33 today, puts it on the table he and Robert, 40, admire it with the foolish expressions of new parents. 'They can be individually adjusted,' explains Robert, with an enthusiasm few could muster for a small piece of plastic. 'You could set it for a level of 10 inches so when the water in the bath rose above that, it would let it out. Or it could be set to two inches. That could save a baby's life.'

Their own plastic baby was born last August when a friend of Trevor's overran his bath, causing pounds 2,000 worth of damage. A few days later, Trevor, lying in the offending bath, thought 'Wouldn't it be a wonderful idea to make a bath plug that kept the water at a level pressure?' Unlike Archimedes, he did not start shouting 'Eureka]' But he did consult friends in the pub. They all said they all knew someone who had suffered a similar disaster, so Trevor, who trained as a mechanic in a Rotherham VW- Audi garage and at Rotherham College of Technology, set about making a prototype.

Myths have already built up around him. 'My girlfriend felt that my obsession was one of the final straws and left,' one paper heart-rendingly quoted him. In fact, his ex-model girlfriend Jane, 24, loyally endured without complaint. What did happen was that his phone was cut off because he could not pay the pounds 740 bill.

Trevor enlisted Robert as his partner. 'People say I grabbed Trevor and said I'd be his partner if he gave me half his money,' says Robert. 'But it's not true. He was the one who offered me half of whatever we made.' That could mean 50p for Robert for every pounds 4.50 plug sold. In England alone there is an estimated market of nine million sales.

The problem is getting it into the bathtubs of the nation. Paul Ambridge, chair of the Institute of Patentees and Inventors, says: 'An invention is coming up with something. An innovation is getting something into the market place. That requires different skills.'

After a high-flying start, Trevor, Robert, Jane and Vikky - Robert's 35-year-old fiancee - discovered this the hard way. Things went swimmingly at first. Their first business meeting was in March with directors of Glynwed International, a Birmingham conglomerate.

'They had very weary expressions, and obviously thought we were going to produce something with cables and levers everywhere,' remembers Robert. 'Trevor opened his briefcase, put the plug on the table and this guy just stared at it for three minutes grinning from ear to ear. He said: 'For 30 years I have had to sit in this office and a sad-faced Yorkshireman and a hippy have come in and turned plumbing upside down'.'

Three days later they met the chairman of the company. Or rather, Robert did. Trevor's car had broken down at Southampton. Robert stumbled alone through the pitch ('I didn't even know how the damn plug worked') and convinced the company to spend three months on plug research. When he left, the chairman ushered him to the lift with an arm draped round his shoulders. In July they filed their patent application and - problem of the lone inventor - had to start spending serious money. The bill for engineering drawings, advice from agents and the patent fee totalled pounds 900, which Robert scraped together with the help of an overdraft.

The axe fell when Glynwed's development contract expired this month and the company decided not to proceed because of doubts about the size of the market and concerns that foreign bodies such as hair would disable the plug. This was a blow. Trevor and Robert are now talking to foreign companies, one of which offered a choice of limousines to pick them up from the airport when they flew over to the US. Negotiations are also under way with two British companies; a meeting is scheduled for next week, when one managing director returns from shooting grouse.

In the meantime, they are struggling with the pressures of fame, turning down interview requests from the likes of breakfast television shows who want to interview Trevor in his bath. They have also been coping with local fall-out. The news that the pair could earn almost pounds 12m a month between them has created resentment in their Isle of Wight home town. Some friends stopped talking to them; others became very affectionate. Both have become weary of plumbers saying cheerily: 'Congratulations] Wish I'd thought of it]'

Although 4,400 patents are filed by lone inventors each year in Britain (in addition to 15,600 by companies), only two per cent go into production. Inventors frequently lose out financially because they cannot afford thousands of pounds a year to maintain worldwide patent fees. Trevor and Robert, who are both very poor and planning to file worldwide patents, prefer not to think about this uncomfortable vision.

If the loot materialises, they have already made a shopping list. Trevor would like a red Ferrari, a 'nice' house and a factory to develop other inventions (other hopefuls have inundated them with ideas, hoping their luck will somehow rub off). Robert wants a bigger powerboat and a 27-acre farm, Trevor's son 'little Trevor' an inflatable and a mountain bike, Vikky an engagement ring.

The big bucks are tantalisingly close. But what if, after the publicity and the limos and the luscious prospect of millions, the dream goes down the drain? Trevor ponders this, then says with Yorkshire pragmatism: 'Well, having never had much money, I'm not that concerned.' But he looks as though it is a sobering thought.

(Photograph omitted)