The canal that let ships skip the top of Scotland

Scotland's north coast has never had a good reputation among sailors. The waters off Cape Wrath and through the Pentland Firth, where the Atlantic meets the North Sea in a scramble of tide and weather, have wrecked ships for as long as ships have tried to pass. For centuries the only way from the Firth of Clyde to the Moray Firth was to go round the top and take your chances, or to unload onto carts and haul everything overland through the Great Glen, the long, dead-straight geological fault that splits the Highlands from Fort William to Inverness.

Thomas Telford's answer, built between 1803 and 1822, was to join the dots. The Caledonian Canal uses three long freshwater lochs, Lochy, Oich and Ness, strung along the Great Glen like beads, and links them with about a third of the distance dug as a proper canal, complete with locks to manage the change in height. At Banavie, near Fort William, a flight of eight locks known as Neptune's Staircase still lifts boats some sixty feet in one go, a piece of engineering built almost entirely with pick, shovel and horse before anything resembling a mechanical digger existed.

A shortcut that arrived a little late

The canal's original purpose was as much strategic as commercial. It was authorised during the Napoleonic Wars, partly so that naval vessels and merchant shipping could avoid the exposed northern route and partly, in the way of many ambitious public works, as a source of employment in a Highlands still reeling from the Clearances. By the time it opened in full, sailing ships had grown larger than its locks could comfortably take, and steamships, when they arrived, mostly found the open sea route fast enough not to need it. The canal never became the trade artery its promoters imagined. It did, however, become one of the most admired pieces of civil engineering in Britain, and it remains navigable from coast to coast, used today mostly by yachts, fishing boats and the occasional small cruise vessel making the crossing for its own sake.

Loch Ness, and the town that watches the water

The middle and longest of the canal's three lochs is Loch Ness, some twenty-three miles of water so deep that it holds more fresh water than every lake in England and Wales combined. Its more famous claim, a monster first widely reported in the press in 1933 and investigated on and off ever since without conclusive result, has done more than almost anything else to put the loch on a world map, whatever anyone privately believes about what, if anything, lives in it. Above the loch's northern end stands Urquhart Castle, ruined since the seventeenth century, which has one of the best claims to the classic view of Highland scenery available from dry land.

None of this is reachable directly by ship: the canal's locks are built for far smaller vessels than a cruise ship, and Loch Ness is reached today by road, on an excursion inland from the coast. The usual starting point is Invergordon, a deep-water port on the Cromarty Firth that has spent the past century adapting to whatever work the sea has offered it. It served as a major Royal Navy anchorage in both world wars, and in 1931 it was the scene of the Invergordon Mutiny, when sailors on the Atlantic Fleet refused duty over a pay cut during the Depression, an episode that rattled the government and reportedly contributed to a run on the pound. Since the oil industry declined, Invergordon has become a base for rig repair and, increasingly, for cruise ships, whose passengers head inland to Inverness, Loch Ness and the Culloden battlefield while the port itself gets on with its quieter modern business.

Which sailings call, and what follows

Fred. Olsen's Scenic Islands and Highlands of Scotland, nine nights from Newcastle, calls at Invergordon on its way to Lerwick, Skye and Orkney, giving a full day for the inland excursion before the ship turns north again.

Shorter sailings use Invergordon as a link in a chain rather than a destination in itself. Ambassador's Legends of the North, five nights between Liverpool and Dundee, calls there between Kirkwall and journey's end, while the longer British Isles Discovery, eleven nights from Tilbury, adds Invergordon to a route that also takes in Stornoway, Orkney, Shetland and Aberdeen.

The canal itself is not something a cruise passenger will sail, at least not on this kind of ship, but standing at Urquhart Castle and looking down the long, glacier-straight line of the loch, it is not hard to see why Telford thought the Great Glen deserved a proper road through it, water and all.