How deep is your lock?

Take a tour of Britain’s deepest, longest, steepest and most unusual canal locks

Image: Dedham Lock/Gideon Chilton


Who hasn’t stopped to admire a lock? The design is ancient and simple: two sets of gates separated by a chamber of water. Yet grinning spectators are a commonplace beside any operational lock. Perhaps it simply makes a picturesque scene. Or perhaps it is the effortless power. Where else but a canal lock can the untrained and unsupervised public be trusted to move tons of water with centuries-old machinery? That’s efficient engineering, right there.

The first locks were built in medieval China over a millennium ago. The idea was picked up in Europe a couple of centuries later, first with ‘flash locks’ that simply flushed boats out in a rush of water, and later with the chambered ‘pound locks’ we still use today. The first in Britain were on the Exeter Canal, completed around 1566, which used three pound locks with lifting gates. The more familiar mitred gates – V-shaped swing gates held together by water pressure – were first devised by Leonardo da Vinci in late 15th-century Milan. They found their way to Britain about a century later, with the mitred gates on the River Lea at Waltham Abbey. James Brindley adapted and standardised the technology in the mid-18th century to create the familiar narrow lock, an important milestone in the progress of the industrial revolution. Brindley’s locks remain the standard today – typically 22m (72 feet) long and one or two narrowboats wide.

Yet not all locks are created equal. Some are deeper, some are wider. Other locks bunch in flights or stairs, while twin locks lie side-by-side. Below, we look at some of the most impressive examples in the country.

Deepest single lock in the UK: Tuel Lane Lock

There are two things that every canal visitor to Sowerby Bridge near Halifax should bear in mind. First is the pronunciation — locals say Sorby not Sowerby. The second is that you shouldn’t, under any circumstances, attempt to open Lock 3.

The Tuel Lane Lock is the deepest in the kingdom, with a 6 metre difference between high and low water. For comparison, a typical double-decker bus is 4.4 metres. Such is the depth, and troublesome proximity to a canal tunnel, that boat crews are not permitted to operate the lock mechanism themselves. Instead, a Canal & River Trust lock keeper is present to help crews negotiate the gates.

The lock is so deep because it does the work of two. It was built in 1996 during restoration of the Rochdale Canal, to more efficiently replace a pair of lesser locks from the original Georgian construction.

Visiting: A short walk from Sowerby Bridge railway station. Boaters: From 13 March until 7 November, a lock keeper is on hand between 8.30am and 5pm on Fri, Sat, Sun, Mon without booking. In winter and on other days, booking is essential. Phone 03030 404040 for details.

Deepest publicly operated lock: Bath Deep Lock

Similar depths are plumbed by Bath Deep Lock on the Kennet and Avon Canal, whose differential is 5.92 metres. This one can be opened by boat crews, making it the deepest publicly operated lock in the country. It is, however, a mere minnow compared with the deepest in the world, found on the River Ertis in Khazakhstan with a 42 metre drop — seven times that at Sowerby or Bath.

Visiting: Bath Deep Lock is close to the city centre and can be visited or operated at any time of day.

Longest flight: Tardebigge Flight and Caen Hill

You need plenty of time on your hands if you’re going to navigate the Worcester and Birmingham Canal. Its 29 mile course contains 58 locks. 30 of them can be found in the village of Tardebigge. It is the longest flight of locks in the UK, raising the water level by 67 metres. The whole suite can take half a day to navigate. Fortunately, the surrounding countryside is rather lovely to contemplate, although it is these same rolling hills that necessitate so many locks in the first place.

Caen Hill Locks on the Kennet and Avon isn’t quite so gate-heavy, with 29 locks, but it boasts a more impressive climb. The series of chambers come in much closer succession than at Tardebigge, elevating the waterway by 72 metres over 2 miles. The main flight of 16 locks is one of the most famous sights on Britain’s waterways.

Visiting: Both flights of locks are manually operated and can be visited at any time. If you’re not in a boat, Tardebigge is most easily reached by car, a short distance from the M5 or M42, or a 2 mile walk from Bromsgrove station. Caen Hill is a pleasant walk west of Devizes, Wiltshire.

Steepest locks: Bingley Five

Flights like Tardebigge are useful for negotiating a gentle gradient, but some canals need to scale heights fast. This calls for that most photogenic of interventions, the staircase lock. These lack any stretch of water between locks; in other words, the lower gate of one lock is the upper gate of the next one down. The steepest example is the Bingley Five Rise Locks, on the Leeds and Liverpool Canal. Boats pass through five chambers and six gates, raising the level 18.1 metres over a length of just 98 metres, a gradient of 1:5. When opened amid thousands of spectators in 1774, the national press described the intervention as “the noblest works of the kind…in the universe”. It remains a popular landmark with sightseers today.

Visiting: the locks are a short work from Bingley station just north of Bradford (you’ll pass a three-lock staircase on the way). Novice boaters might be pleased to hear that the intimidating sequence is controlled by a lock-keeper, on hand during daylight hours without prebooking.

Most unusual lock: Falkirk Wheel

If you thought the great age of lock engineering was strictly in the past, pay a visit to the Falkirk Wheel. It isn’t technically a lock, but it serves the same purpose. The landmark structure connects the Forth and Clyde Canal to the Union Canal (Falkirk to Edinburgh) and is truly a modern marvel of engineering, raising boats by 24 metres with plenty of bravado. A boat may enter the wheel as with any regular lock. Rather than adjusting the water level to raise the boat, the structure turns on its axis like a giant ferris wheel, plucking the boat out of the lower canal and arcing it round to the upper level (or vice-versa). The wheel was built at the turn of the 21st century as a Millennium project, to reconnect two long-separated canals with deliberate spectacle. Such was its impact that the wheel now features on the back of the Bank of Scotland’s £50 note – a rare accolade for canal infrastructure.

Visiting: The wheel is a prominent tourist attraction, with almost half a million visitors each year. It boasts its own visitor centre, with regular boat trips up through the wheel. Tickets are £12.50 (adult), £11 (concession), £7.50 (children aged 3-15) and £1.50 (under 3). The visitor centre, open daily, is geared up for families, with miniature canals, model boats and a giant aquatic map of Scotland.