Arms and locks

THE GRAND UNION canal, constructed from the late 1790s onwards, is an important artery of England’s canal network. Beginning at Brentford on the River Thames, it winds its way to Braunston and Birmingham. Along its way it meets other canals, some of which are designated ‘arms’. For example, the Paddington Arm joins the main canal at Bulls Bridge in west London and from there it makes its way eastwards to Paddington. Recently, we visited friends, who live in Northamptonshire, and they took us on a walk along another arm of the Grand Union, the Northampton Arm. This branch of the main canal begins near Gayton and Blisworth and runs to nearby Northampton, where it enters the River Nene, which flows eastwards towards The Wash, an enormous inlet of the North Sea.

A swing bridge with a lock behind it

Much of the Northampton Arm is very narrow, just wide enough for passage of a single narrow boat. At regular intervals, the arm widens to allow vessels travelling in opposite directions to pass each other. Though short in length, only 4.6 miles, the Northampton Arm has seventeen separate, hand-operated locks for vessels to negotiate. The twelve of these, a flight of locks, is 1123 yards from the Gayton junction with the main canal. These twelve locks are along a stretch of canal only nine tenths of a mile long. The northernmost lock, that nearest towards Northampton, is a few yards north of a bridge carrying the M1 motorway. The locks carry the water from a bit over 300 feet above sea level nearest Gayton down to less than about 225 feet, each lock capable of lifting or lowering a vessel over 6 feet on average. Nearer Gayton, there is an old swing bridge, rather like a castle’s drawbridge. Looking at old maps, it appears that there were several more of these along the arm, but we only spotted one in the stretch between Gayton and the M1.

The canal and its associated towpath pass beneath the motorway through a giant concrete arch, paraboloid in shape and reinforced with horizontal concrete beams. Lined with graffiti, both conventional and anarchic artwork, walking under the motorway is an eery, rather science fictional experience. In contrast to this brutalist concrete arch, several lovely brick, hump-backed bridges carry minor roads over the Arm

The authorisation of the Northampton Arm was given in 1793, but it took another 18 years before it was ready for use. A brief hstory of the Arm (https://waterways.org.uk/waterways/discover-the-waterways/grand-union-canal-northampton-arm) relates:

“Almost immediately the Arm began to carry a large volume of merchandise and stayed busy for over 100 years through to after the First World War.  In the post war years coal, grain and timber were supplemented by goods needed for the show industry such as strawboards for packing as well as iron ingots for castings.  After World War II the carriage of goods ceased as road competition strengthened.”

Now, the Arm is used by intrepid canal boat owners, who are not averse to too much manipulation of lock gates. On the sunny Saturday afternoon that we visited the lock flight, we only saw one narrow boat attempting to negotiate the flight of twelve locks. In contrast, at Gayton Junction, the main Grand Union Canal, from which the Arm branches off, was full of pleasure-seekers’ narrow boats and other craft.

Though hardly used for freight these days, the canal system provides much pleasure to visitors both afloat and on shore. Wandering along the towpaths, one cannot fail to be amazed when considering the engineering ingenuity of the canal builders that we can still see today, as well as the work that is done to keep these waterways usable so many years after they were constructed.