LEES looked down into the amphitheatre where the moon couldn't reach and tried to calculate the length of the drop. Behind him the others were uncoiling the ropes while the injured man muttered in delirium, and the survivor (who had been stranded here for many hours) watched and waited, torn between interest and relief.

When they tied the casualty on Lees' back, his heart sank, for although he was a big man, his load was heavier. He could scarcely stand upright and suddenly to be on a ledge halfway down a cliff on a winter's night with fourteen stone on his back seemed utterly fantastic. Below them the wall dropped like a plumbline; close to two hundred feet, he reckoned, and all in the black moon-shadow.

The angle worried him less than the distance. Technically, if not psychologically, the steeper the better, as there would be no ledges to impede progress - although, of course, after a few feet both rescuer and his load would start to twist and swing; then he would be fighting to keep himself as a buffer between the casualty and the rock (another blow on that fractured skull would surely kill the man) and he would think of the breaking strain of nylon rope.

But this was unreasonable, he thought; he was strong enough to keep the patient off the rock, and nylon didn't break - unless shock-loaded or running over rock under stress . . .

The extent of the drop was a different matter; it was well over 120 feet and this was the length of a rope. So ropes had to be knotted together, and it was this that made the whole proceeding - and that of similar rescues - so dangerous. Should a knot catch or jam in a crack the rescuer will dangle, with his load doubling the weight. He cannot be lowered or pulled up, particularly if he is under an overhand.

As Lees stood there pondering the knots and the drop, Robertson, now tied firmly on the guide's back, became aware of his unusual position and started to struggle. There was nothing for it but to start. Lees lowered himself until he was half-sitting, half-lying on the edge. He looked up at the men he had trained, saw their bodies tense as they waited for the load, and he started down.

Bray had Lees' rope, Andrews had Robertson's. But Bray was in such a position that he couldn't take Lees' weight until the guide was over the edge. As if this, the most difficult move of the operation, were not dangerous enough, at this crucial moment Robertson was clawing wildly at his rescuer's face, dislodging the headlight and threatening to tear it off altogether. Lees didn't stop but continued down until Bray was taking the strain. Now they were on the wall and Robertson, as if realising through his delirium that they were committed, quietened. Then there was no sound but the angry snap and tear of the ropes grating along the edge as they found the shortest line - and the screech of his boot nails as Lees fought the rock.

Then, about thirty feet down, they called to him to stop, because his rope was running through a crack in some boulders and they must try to flick it free, for this was where the knot would jam. But, owning to the strain on the rope, freeing it was impossible, and it had to be left.

They heard him say he was continuing straight down the wall, and then he passed out of sight. Immediately all contact was lost, for any shouting resulted in confused echoes running round the amphitheatre, and as a result it was impossible to synchronise the lowering. They could judge only by the feel in the rope if they were lowering Lees slightly below Robertson. In this way Andrews should be taking most of the casualty's weight. Nevertheless, sometimes Lees was hanging from Robertson, and at others the position was reversed, to the guide's intense discomfort.

By now the lowering stance was in the moonlight and, after Lees had gone nearly a hundred feet, Bray saw the knot in the rope coming up to him from the coil on the ledge. It went through his leather gauntlets and he saw it start to descent to where it was going to jam in the crack. He was about to ask the survivor to take over from him so that he could climb down and attempt to stop it jamming in some way when the rope stopped moving. He glanced at Andrews' rope. That was still too.

Shouts echoed round the buttresses, then they heard, quite clearly:

"I am in the amphitheatre," and the rope went slack. The knot was one foot from the cleft in the boulders.

They relaxed and flexed their aching muscles. They opened their hands with difficulty and looked at the polished black grooves in the palms, and then they realised that it was so cold that the gauntlets were frozen. They started to coil the ropes, and to climb slowly back to the top of the cliff, taking the survivor with them. They were hungry and tired and uncomfortable - and so cold that there was little feeling left in their feet or hands. Ahead of them lay the long carry over miles of untracked bog where speed was imperative if the whole dangerous operation was to be successful - and the fatigue, the cold and the acute discomfort were all immaterial, for they were justifying their existence: not a corpse this time, they were bringing two men down - alive.