The broad canal from the Thames at Brentford to Birmingham, 137 miles over the Chiltern summit at Tring
The Grand Union is the main canal route between London and Birmingham, running 137 miles from the River Thames at Brentford up over the Chilterns and down through Warwickshire to the city centre. Much of it is a broad canal, its locks built wide enough for two narrowboats side by side, and there are 158 of them on the main line. From the Thames the canal climbs through some 50 locks to its summit level at Tring, a three-mile pound cut through the chalk of the Chiltern hills, before working its way north and west.
It is not a single old waterway but several joined together. The Grand Union was formed in 1929 by amalgamating a string of older canals — chief among them the Grand Junction from London to the Midlands — into one company, which then spent the 1930s widening locks and improving the line to compete with the railways. The Hatton Locks near Warwick, a flight of 21 known as the Stairway to Heaven, date from that rebuilding.
The engineering highlights are mostly the work of the older canals it absorbed. Blisworth Tunnel carries the canal 3,057 yards through the Northamptonshire hills, one of the longest navigable canal tunnels in the country, and the junction at Braunston remains the busy hub of the system.
The towpath is continuous and level, which makes it a straightforward long walk or cycle, and the line is easy to reach — it passes Watford, Tring, Milton Keynes and Warwick, several on the railway. Arms branch off to Leicester, Paddington, Northampton, Aylesbury and Slough.
