The cruelly jagged peaks of Skye's Black Cuillin inspire both awe and fear, inviting man to struggle with the infinite. It's all downhill from here

For the mountaineer, there is nowhere in Britain to rival the Black Cuillin of Skye. Some would say nowhere in the world. The "rocking antlered Cuillin", as the island's poet Sorley MacLean once described them, appear freshly risen from the Sea of the Hebrides to form an irresistible invitation to climb.

For the mountaineer, there is nowhere in Britain to rival the Black Cuillin of Skye. Some would say nowhere in the world. The "rocking antlered Cuillin", as the island's poet Sorley MacLean once described them, appear freshly risen from the Sea of the Hebrides to form an irresistible invitation to climb.

At the heart of the six-mile-long Cuillin ridge rises the Inaccessible Pinnacle, or In Pin to its suitors. A fearsome dorsal-fin rock, the pinnacle is the stuff of recurrent nightmares for those poor souls afflicted with "Munrosis", a craving to climb every peak of more than 3,000ft in Scotland. This obsessive disorder takes its name from Sir Hugh Munro, a king's messenger, who first tabulated all the peaks over the magic figure. After various revisions by the Ordnance Survey, there are now 284 distinct Munros. Sir Hugh failed to complete his own list by three peaks when he died in 1909. His most glaring omission was the dreaded Pinnacle of Skye.

Guidebooks summarise the perils of the In Pin by saying that it is the only Munro where a rope is a necessity and where walkers are advised to engage the assistance of a rock climber. One Victorian description of the In Pin's East Ridge reads: "A razor-like edge with an overhanging and infinite drop on one side, and a drop longer and steeper on the other." That's if you take the easiest route up.

My mission was to take the former medical editor of this newspaper, Oliver Gillie, up the Inaccessible Pinnacle. Even allowing for an element of hyperbole, Oliver was impressed by the "infinite drop" quotation. Aged 62, he was a latecomer to Munro-bagging and had decided to tackle the hardest early on.

May and June are the best months for Cuillin climbing, with the best chances of high pressure and long, clear days. But there are no guarantees. On our first visit in 1999, it snowed right down to the sea and we had to hide in a bookshop. Though the next day dawned dazzling, the In Pin was out of the question. Instead, we climbed Bruach na Frithe, another 3,000 footer along the ridge. Brushing fresh snow off footholds, Oliver fantasised about the comforting "thwock-thwock" of a rescue helicopter.

On our return early this summer we found ourselves in the odd position of viewing property that was up for sale. John MacLeod of MacLeod had put the Cuillin on the market for £10 million, to finance the repair of a leaking roof on his ancestral home, Dunvegan Castle. The 22,300-acre plot included the In Pin, 10 other Munros and nine further subsidiary tops more than 3,000ft high. Maybe we were not the most serious of prospective purchasers, but at least we could relieve the plod across the boggy moor to the foot of the Cuillin with a rumination on the ownership of mountains. Is it morally right that one person can lay personal claim to a wild mountain, let alone a whole range?

To the photographer and author Gordon Stainforth the idea is "obscene". Stainforth's book The Cuillin is a marvellous evocation of the mystery and severe majesty of the range. He spent 150 days in all weathers on location without ever thinking that this gift of the Earth's elemental forces was someone's possession. Now he's angry that it will simply go to the highest bidder.

It's not that the 29th Chief of the MacLeods had been a bad landlord. Far from it. And he insisted that any new owner must continue to allow unfettered public access. But the proposed sale had put fire in the bellies of Scotland's land reformers at a politically crucial time. MacLeod had not only brought down a storm on his own, perhaps naïve, Old Etonian head but pencilled in a question mark over the ownership of many of Scotland's other mountain tops.

MacLeod traces his line back to the 13th century and the arrival at Dunvegan of Leod, son of Olaf the Black, King of the Isle of Man. The Cuillin's role in family history was mainly as a tribal battleground. In Harta Corrie stands the Bloody Stone where the MacLeods made a vain stand against their arch-rivals, the MacDonalds. All of them were killed and their bodies piled up round the fateful boulder.

The Bloody Stone's inclusion in the sale underlines the belief that this is clan land rather than a personal fief. Scrambling up the scree of Sgurr Dearg on our approach to the In Pin, Oliver suggested that clan ownership might be the ideal solution; a kind of MacLeod Trust that could also fix the castle roof. But the MacLeods have been scattered to the corners of the earth for generations, while communities around the Cuillin have grown afresh with incomers from mainland Scotland and England. Ironically, while MacLeod gets next to no income from the Cuillin, the small local townships feed well off the thousands of climbers and visitors the mountains attract. Community ownership would be the radical way.

A good deal of mist surrounded MacLeod's own title to the Cuillin, said to rest on the Dunvegan charter of 1611. Unfortunately for the chief, the royal document set no boundaries and made no mention of the Cuillin. At least one legal expert suggested that MacLeod only owned the farmland and useful valley bits, leaving the peaks in the hands of the state. This is the case with 63,000 acres of so-called "mountain wastes" in Wales. Land reformers fantasised that lairds right across the Highlands might not own the high tops they lay claim to and, remarkably, the Crown Estate Commission began an investigation into MacLeod's title. But revolution does not course through the veins of commission lawyers, and they dropped the case last month. The sale could go on.

But never mind lawyers and estate agents. The Cuillin is, perhaps, best appreciated by poets and climbers. Sorley MacLean saw the great ridge as a symbol of man's heroic spirit rising above the tawdry. Our potentially heroic spirits this year included Oliver's second cousin, a 60-year-old former metals trader, and my son, 21, a trainee outdoor-pursuits instructor.

Traversing the serrated crest of the range took one long, exhausting day. But, exploring the Cuillin's remote corries and crags lasts a lot longer. Part of the attraction is the wonderfully adhesive rock, a coarse-grained volcanic stuff known as gabbro.

We came upon the pinnacle quite suddenly and, having scrambled over the top of Sgurr Dearg, there it was; a razor of gabbro rising from the eastern slope of the main hill. In the cold mist, the 50ft-high blunt edge rose above us like the dripping prow of a ship. Oliver quaked inwardly. Perhaps we all did.

"There it was, a huge, grey hulk, wet and slippery. It was rather ominous," Oliver recalled. "If it had proved we couldn't get up that day, I would have probably felt quite relieved." We skulked about beneath this edge for a while. It offered shelter from the squalls of sleet and snow, but the steep rock was horrendously greasy. Whatever the wind, the alternative East Ridge - that of the "infinite drop" - was the only practical option.

In fine weather, the East Ridge is a delicate stairway with sensational exposure; in the wet, the polished holds required extra care. However, for most of the climb the swirling cloud afforded comfort to the party by denying us a plunging view. When the vapours briefly parted, one reaction was "Bloody hell, don't stop to admire the view. Let's just get to the top as fast as possible." It was a case of follow the rope and stick to the rock, even if that meant sitting astride it à cheval for a few dizzying feet.

The chief of the MacLeods has been here too. A self-confessed non-climber, he was taken up the pinnacle many years ago and found it "quite extraordinarily exciting". I questioned whether he knew what a priceless thing he was selling. But he told me: "Frankly, that half-hour climb was one of the most exciting and wonderful things I have ever done. Sheer magic." His pain at putting the Cuillin on the market seems genuine enough.

For ourselves, though, the machinations of Dunvegan had been cast aside. Oliver was hauling himself up the last step of the ridge, and moving tentatively over an inclined slab to touch the coveted summit block. The other two weren't far behind. All that remained was a 50ft abseil off the blunt edge. The Inaccessible Pinnacle was ours already.