Brentford To Braunston
One end of the Grand Union Canal (Grand Junction Canal - Main Line) is at Brentford on the River Thames in west London, where the canal follows the engineered course of the River Brent. The double Thames Lock at Brentford acts as the demarcation point between the Thames, administered by the Port of London Authority, and the River Brent/Grand Union Canal, administered by British Waterways. The locks on the canal are numbered south from Braunston, and Thames Lock is lock number 101.
From the Thames Lock, the canal and the River Brent are one and the same, and the waterway is semi-tidal until the double Gauging Lock (lock 100) at Brentford is reached. Just upstream of the Gauging Lock was a large canal basin, now known as Brentford Lock, from which the canal continues to follow the course of the River Brent through two more locks. The river and canal part company at the base of the Hanwell flight of locks (92-97), before two more locks take the canal to Norwood Green. It then heads westward over level ground through Southall, Hayes and West Drayton until it reaches the valley of the River Colne where it swings northward to Cowley through Uxbridge.
Three miles (5 km) from Norwood on this long level is Bulls Bridge Junction, once the site of the Grand Union Canal Carrying Company's main dockyard. At Bulls Bridge, the Paddington Arm branches off to the north and runs 12 miles (19 km) to join the Regents Canal at Little Venice (see below). Just before Uxbridge is Cowley Peachey junction, where the Slough Arm branches off westward.
At Cowley, the canal begins to climb the valley of the River Colne following a north-westerly course to Uxbridge After Denham and Harefield, it passes to the south of Rickmansworth. Here it merges with the Rivers Chess, Colne and Gade. After Rickmansworth, the canal follows the valley of the River Gade, a tributary of the River Colne, passing the site of Croxley paper mill. The canal skirts Watford through Cassiobury Park, passing under the M25 motorway as it approaches Kings Langley.
By now the locks are becoming more frequent as the climb into the Chiltern Hills steepens. The original four locks here were replaced in 1819 by five shallower ones to alleviate problems with water supply to the nearby paper mills. This realigned the canal to the south of its former course; the locks here are still referred to - without irony - as "The New 'Uns" by traditional boaters, and the term has been passed on to a new generation of canal users.
After Kings Langley and Apsley - the site of more former paper mills - the canal passes Hemel Hempstead and Boxmoor Common. From here the canal follows the course of the River Bulbourne through Bourne End with the well-known swingbridge at Winkwell, and the "Port of Berkhamsted". At Cow Roast Lock the canal reaches the 3-mile (5-km) long summit level at Tring in the Chiltern hills, having risen through 54 locks since Brentford.
At the north-west end of the summit level is Bulbourne Works, where lock gates were manufactured until 2003 for the southern canal network. Half a mile (800 m) further on, the canal reaches the top of the Marsworth flight of seven locks, which begin the descent to the Vale of Aylesbury. The Wendover Arm branches off westwards from the summit level under a bridge adjacent to Marsworth Top Lock and is currently navigable for just over a mile to moorings and a winding hole. There is a restoration project to extend it back to Wendover. This part of the canal in parlance used by natives and canal staff was "the withered arm" and in fact was only really "opened" to allow the pumping station there to pump water into the summit. A few hundred yards (metres) beyond the bottom lock of the flight, the Aylesbury Arm branches off to the south west.
The Grand Union crosses the wide valley gradually, descending by interspersed locks past the villages of Cheddington, Horton and Slapton until it reaches Leighton Buzzard. Traditionally this section of the canal is called "Slapton Fields" or just "The Fields" by boaters.
A few miles further on it enters Milton Keynes at the outskirts of Bletchley at Fenny Stratford Lock, which is unusual in lowering the level by only 12 inches (30 cm). The next stretch of 11 miles (18 km) on the level takes the canal through the new city, where there is a marina. (There is a plan (see below) to dig a new arm from here to the Great Ouse at Bedford). North of the centre, it traverses the modern New Bradwell Aqueduct, the first on the Grand Union in over 100 years. Leaving Milton Keynes at Wolverton, the canal runs on a high embankment before passing over the Great Ouse at Cosgrove "Iron Trunk" aqueduct.
After rising through Cosgrove Lock, (and passing the start of the abandoned Buckingham Arm) another long level section brings the canal to the bottom of the Stoke Bruerne flight of seven locks. At the top of this flight is the Stoke Bruerne Canal Museum followed shortly by Blisworth Tunnel, at 3056 yards (2794 m) one of the longest on the canal network.
Once clear of the tunnel, the canal passes Blisworth village and reaches Gayton Junction where the Northampton Arm branches off to the east. This arm has seventeen narrow locks as it descends to join the navigable River Nene (see below). The long level stretch continues past several villages including Nether Heyford and Weedon Bec and is very rural in character.
At Whilton, the canal reaches the bottom of the Buckby flight of seven locks which raise it to Braunston summit although the village of that name is still 5 miles (8 km) distant. Beyond the top lock is Norton Junction where the Leicester line (not strictly a branch) heads off north. A few miles further on the canal passes through the 2040-yard (1865-m) Braunston Tunnel, which pierces a low range of hills that are part of the Northamptonshire uplands.
The canal then drops down the Braunston flight of six locks until it reaches Braunston Junction, just over 93 miles (150 km) from Brentford.
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