The engine was discovered in 1983 by Jeremy Landless, 48, a former RAF engineer and frustrated pot-holer, in the old Glencrieff mine at Wanlockhead, Dumfriesshire. Operated by hydraulic power, the engine was made in 1833 and was installed at Wanlockhead to pump water out of deep mine workings.
Mr Landless and his friends had to abseil down a 100ft shaft, balance on a ledge and then descend another, 80ft, shaft. They then wriggled through 12ft of fallen rock and, entering a small tunnel, walked, bent double, for 800ft to reach the pumping room which contained the engine.
Mr Landless said: 'One of its castings had been broken and repaired. We believe that the break which we saw is evidence of a bitter dispute between workers and management at the mine.'
Detective work in the archives found that the South Glencrieff engine was probably used first in 1833 in another part of the mine, the North Cove seam. And a letter, written in 1833 by J B Stewart, the senior overseer at the mine, alleged that a large stone had been thrown into the mechanism of the engine at North Cove causing serious damage. The damage was evidently repaired and the engine moved to the South Glencrieff seam.
Gilmour Harris, 58, a retired engineer and trustee of the Mining Museum at Wanlockhead, went on a six-month diet and lost 2st so that he could make the underground journey to see the engine. His grandfather worked in the mine and he was determined to visit the engine. But when he descended the 100ft shaft last summer he found that the lower level was flooded.
A rock fall had caused the flooding and blocked access to the engine. But Mr Landless was not deterred, deciding they must burrow into the mountain along an old drainage tunnel to reach the engine once more. Assisted by Mr Harris and Charlie Smart, 53, a motorcycle policeman who has retired to Wanlockhead, Mr Landless reckons that it will take the three men four years.
They must wade through a stream and crawl on hands and knees into a hole in the side of the mountain to start their work. Each day they burrow two or three feet forward, shifting the rubble on a railway which they have built. The rotting timbers of the old workings might collapse at any moment, so as they edge forward they make the sides secure with new timbers.
The engine is expected to be listed by Historic Scotland as an important artefact that should be preserved. It was built sometime before 1833 by 'Mr Dean of Hexham', Northumberland, a small manufacturer of mining equipment. It was a double acting engine - it had a large cylinder filled alternately with water, first from one end and then from the other. The water, gathered from streams in the surrounding hills, came under pressure from a tank 136 feet above the engine.
It replaced an earlier Watt steam engine in the North Cove seam. Hydraulic power was cheaper than steam and enabled the mine to compete with imports of cheap Spanish lead.
'There are at least four rock falls between us and the engine and each of them is about 12 feet long,' Mr Landless said. 'When we get there we are not sure what we are going to do. I don't think we should leave the engine underground because only a few ardent potholders would be able to get to it. It is so important in industrial archaelogical terms that the public should be able to see it.'