TO the cavers who were called out to probe the hole in the ground at Darnbrook Farm in July 1975 - like Harry Long, of Silsden - it was literally a step back to a moment frozen in time.

For the writing they discovered on the walls - the names of five men who had last ventured into the subterranean depths - was "as fresh as the day it was written," recalled Harry when we recently spoke to him about the adventure.

And had these early cavers taken down a bottle of beer as their refreshment? Among their leftovers was a pint bottle marked Taylors of Lancashire.

Harry, a Craven Pothole Club member, along with fellow members, reporter Ian Plant, later editor of the Craven Herald before he tragically drowned in a cave in 1980, and Dave Hodgson, scrambled underground after being alerted to the hole by Dave's friends, the three Robinson brothers, who had farmed at Darnbrook for 33 years before moving to Grassington.

"What we found was astonishing. The names scratched in the rock were as fresh as the day on which they had been written.

"We also saw the marks of corduroy trousers imprinted in the mud making it clear where they had progressed.

"There was also a pile of stones which had obviously been moved by someone to make progress. It was as if it had happened the day before," said Harry.

One of the names was W.Morrison, dated 1867. It was the same Walter Morrison who later became Skipton's MP and funded the book Craven's Part in the Great War, a record of the men who fell in the conflict between 1914 and 1918.

His mountain home was on Malham Moor close to the Darnbrook "estate" on the fell towards Arncliffe.

There is a photograph of magnificently bearded Walter, who then looks in his late 60s, on the second page of the volume which was published in late 1919.

He had taken over Malham Moor estate in 1860 and among the three men who ventured underground with him in 1867 was his head gardener, Thomas Coulthard, his estate gamekeeper William Ward and Litton farmer J Lee.

The two others, J Metcalfe and John Gill, who farmed at Litton, had gone down five years earlier. All had left their moniker for posterity on the cave walls.

The re-discovery of the pothole, later named Robinsons Pot, came as workers renovating the house found an area of damp in the kitchen. The farm was then owned by Littlewood Pools heir John Moores and is now cared for by The National Trust.

"On investigating they came across a slate which went under the wall of the house. When they looked outside, they spotted and archway of stone and the extension of the piece of slate.

"They broke through and exposed a big black hole. It appeared as if the house had been built over the pothole," said Harry.

In 1975, the team of explorers, led by Dave Hodgson, who had been investigating Darnbrook area for signs of caves for some time, first saw the "insignificant" hole in the flags at the side of the kitchen wall in the farm yard.

He descended on a pothole ladder to a rocky floor about 20ft below and set off along an undulating dry passage and after 70ft, came to the brink of a short climb down into a chamber. He scrambled down to where a stream welled up from the floor and sank amidst boulders .

It was here, to his amazement, he discovered the names scratched into the walls and in the mud on the ground, the print of corduroy trousers, footprints resembling clogs and an old bottle marked Taylors of Lancaster, one imperial pint.

Returning to the surface, Dave was joined by Harry and together they entered a series of muddy and sandy crawls carrying a small stream and arriving at another which flowed into a bedding plain. They guessed that it was unlikely the earlier explorers had reached so far.

Later, they were accompanied by other cavers and eventually they passed into a 50ft high chamber. The stream flowed into a low tunnel where the roof met the water.

Next day other cavers moved on into an 800ft long sandy and muddy passage, ending in a boulder choke.

This was the start of a comprehensive exploration of the system which unearthed a huge stream passage carrying a river. The cavers believed this was the main underwater drainage of Darnbrook Fell.

Upstream there was a 600ft canyon stream-way ten feet wide and between ten and 15ft high.

In the weeks that followed, passages were mapped and photographed and samples and specimens collected including seven species of caddisfly at larvae and nymph stages, bones of a small rodent and a piece of antler.

A National Trust spokesman said Darnbrook Farm was a tenanted National Trust Farm and the Northern Caving Clubs had a licence agreement to use it a limited number of times per year.

The charity was aware of the writing on the walls and that Walter Morrison was linked to Tarn House and the Malham Tarn Estate.