Neptune’s Staircase: Eight Locks on the Caledonian Canal

At Banavie, a few miles north of Fort William, the Caledonian Canal comes down to the sea in one long, deliberate stride. Neptune’s Staircase is a flight of eight locks built by Thomas Telford, set end to end along a quarter of a mile of granite masonry, with Ben Nevis filling the skyline behind. It lowers the canal about 19 metres (62 feet) towards Loch Linnhe and, according to Scottish Canals, is the longest staircase lock in Scotland. The group stands beside it on the twelfth day of our Canals and Railways in the Industrial Revolution tour, just before boarding the West Highland Railway, and it is one of the clearest places in Britain to see how engineers answered the question of moving a ship up a hillside.

A canal through the Great Glen

The Caledonian Canal follows the Great Glen, the long, straight geological fault that cuts Scotland diagonally from Fort William in the south-west to Inverness in the north-east. Nature had already done much of the work. Four lochs lie along the glen, Loch Lochy, Loch Oich, Loch Ness and Loch Dochfour, and the canal links them with cuts and locks to make a 60-mile route between the west coast and the Moray Firth.

The case for building it was made during the Napoleonic Wars. Ships sailing between the east coast and the Atlantic otherwise had to round the north of Scotland through the Pentland Firth, a passage feared for its tides and weather, and a protected inland route also kept vessels out of reach of French privateers. Telford agreed to size the locks for the navy’s 32-gun frigates. There was a social purpose too. The Highlands were losing people to emigration, and a government-funded public work offered paid employment to men who might otherwise have left.

Parliament passed the Act in July 1803. Thomas Telford was principal engineer, with William Jessop as consulting engineer, and the southern section, including Banavie, was supervised by a resident engineer named John Telford, who was no relation.

The problem at Banavie: getting down to the sea

A canal that uses lochs as part of its route inherits their levels. The summit of the Caledonian Canal is Loch Oich, 106 feet (32.3 metres) above sea level, and from there the water has to step down in both directions, to the Moray Firth at Inverness and to Loch Linnhe at Corpach. In all, 29 locks do the work.

At the western end the descent is concentrated close to the sea. Between the canal’s level at Banavie and the sea locks at Corpach the ground falls away steeply, and Telford chose to take most of that drop in a single flight. The usual way to climb a slope is a series of separate locks with stretches of level water, called pounds, between them. The sixteen Marple Locks on the Peak Forest Canal, which the group sees early in the tour, work that way, spread out down a hillside in Greater Manchester. At Banavie there was no room for pounds, so the locks were built touching one another.

How does a staircase lock work?

A staircase lock is a run of chambers in which the top gate of one chamber is also the bottom gate of the next. There is no pound between them, so a boat climbing the flight moves directly from one full chamber into the next as each pair of gates opens. Water is let down from chamber to chamber in the same way, so the whole flight has to be worked in a careful order, with the keepers making sure no chamber is overfilled or drained before the next is ready.

The scale at Banavie is large. Each chamber is 180 feet (55 metres) long and 40 feet (12 metres) wide, built for sea-going ships rather than the narrow boats of the English canals. Together the eight locks lower the canal about 19 metres. Today’s gates weigh 22 tons each, and Scottish Canals says a boat takes about 90 minutes to pass up or down the flight.

How long does it take a boat to go through Neptune’s Staircase?

About 90 minutes in either direction, according to Scottish Canals. When the flight was worked by hand the passage took just over half a day. Because boats move through the chambers in convoy, a visitor who arrives as a group of vessels is entering the top or bottom lock can watch the whole sequence unfold while walking slowly beside them.

From capstans to hydraulics

For almost a century and a half, the gates were opened and closed by muscle. The flight had 36 capstans, two to each gate leaf, each turned with four wooden poles, and it took seven full turns to open or close a gate. Working a vessel through all eight locks meant 126 turns of the capstans, which is why the passage once took half a day.

The Caledonian Canal passed to the British Waterways Board in 1962, and mechanisation followed. By 1969 every lock on the flight had been fitted with hydraulic rams and push-button controls. Even so, the flight still needs at least three lock-keepers to run it, and the staircase remains a place where you can watch a canal being worked by hand-eye judgement rather than by an automatic system.

Building in hard country

The work went slowly. Three of the Banavie locks were finished by June 1809, three more followed, and the last two were complete by the end of 1811. The rest of the canal took another decade, and it finally opened in October 1822. The original estimate had been £474,000; the eventual cost was about £910,000, and construction ran twelve years over schedule. To save money the planned depth of 20 feet was reduced to 15 feet, a decision that would come back to haunt the canal as ships grew larger.

The masonry caused trouble too. An engineer’s report of 1837 condemned it, and the Banavie flight needed major repairs in 1880 and 1910, and again in 1920, when a Ministry of Transport grant of £11,000 paid for work that closed the canal for nine weeks. In 1929 a drifter broke two lock gates, flooding the flight and stopping traffic for three months. The canal’s most recent rescue came between 1995 and 2005, when engineers spent ten winters drilling and grouting the old structures rather than rebuilding them.

Commercially, the Caledonian Canal never met its promoters’ hopes. By the time it was deepened in the 1840s, steam-powered iron ships were outgrowing it. Passenger traffic did better. As early as 1824 a lock house at Banavie was converted into an inn for steamboat passengers, and Queen Victoria’s voyage along the canal in 1873 brought it a wave of visitors.

Where road and railway cross the canal

At the foot of the staircase, the road and the West Highland railway line cross the canal on swing bridges. Telford and Jessop rejected lifting bascule bridges here because they feared ships’ masts would be damaged, and chose bridges that pivot sideways to clear the channel. The railway crossing makes Banavie a well-known spot for watching trains as well as boats, and Scottish Canals notes that it is a favourite place for gongoozling, the old canal word for watching boats go by.

How far is Neptune’s Staircase from Fort William?

About four miles north of the town, in the village of Banavie. Public access is free and open at all times. The western end of the canal lies close by at Corpach, where the sea lock opens onto Loch Linnhe; the engineers there had to build on rock and use a steam engine to keep the works dry while the lock was constructed.

How much walking is involved at Neptune’s Staircase?

Very little is required, though more is possible. The flight runs for about a quarter of a mile, and a path follows it on the bank, so you can see the locks from the bottom near the road or walk the length of the staircase at your own pace. The path forms part of the Great Glen Way, and Scottish Canals lists accessible access at the site. The tour as a whole is rated Level 2 (Moderate), with three to five hours of activity on most days.

Neptune’s Staircase on the tour

The Scottish leg of the itinerary is built around the waterways. The day before Banavie, the coach travels north from the Lake District, stopping at the mill village of New Lanark, then continues past Loch Lomond and through Glencoe to Fort William for the night. On Day 12 the group takes the bus out to Banavie to see the staircase and the swing bridges, then boards the West Highland Railway between Fort William and Mallaig, a line of viaducts and tunnels that includes the Glenfinnan Viaduct. After a stop at the Glenfinnan monument and visitor centre, the day ends with a drive through the Trossachs to Stirling.

The next morning brings the other great Scottish answer to a change of level. At Falkirk, the rotating boat lift of the Falkirk Wheel reconnects two canals that were once joined by a flight of eleven locks. Seeing the two a day apart is a lesson in how engineering thinking changed between Telford’s generation and the Millennium Link. For how these sites fit into the route as a whole, from the Midlands through Wales and the north of England to Scotland and back to London, see our guide to Britain’s canals, railways and industrial heritage.

The tour runs for 23 days from Manchester to London in small groups of 6–14 travellers, with departures in April and September 2027. You can read the full day-by-day itinerary on the Canals and Railways in the Industrial Revolution tour page.

Two centuries after the first gates were swung by hand, Neptune’s Staircase still does exactly what Telford built it to do. Standing at the top of the flight, with the canal dropping away towards the sea and the mass of Ben Nevis behind, it is easy to see why this short stretch of masonry has become one of the defining sights of the Highlands’ industrial past.