Guide to Grand Union Canal

The Grand Union Canal is the longest canal in the UK spanning across several counties and linking the major cities of Birmingham and London.

A brief history of the Grand Union Canal

The Grand Union Canal started life as the Grand Junction Canal, built at the end of the 18th century, allowing the key towns and cities of the Midlands to send goods from the Birmingham navigation to the nation’s capital.

Gradually between 1894 and 1929  several independent waterways — the oldest being the navigations around the River Soar in Leicestershire, the longest the Grand Junction Canal from Braunston to the River Thames, were amalgamated into the Grand Union which includes a huge flight of locks.

The term ‘Grand Union’ is now generally taken to mean the canal from the Thames at Brentford to the junction with the Digbeth Branch in Birmingham to the Birmingham Canal; see our canal map below.

The canal network now is used predominantly for leisure activities such as boat hire, canal boat holidays, boat moorings as well as sports and activities such as canoeing and paddle boarding. There is also a Grand Union canal walk route alongside parts of the waterway.


Top Grand Union Facts

  • Main Line Canal Length

    137 Miles

  • Number of Locks


  • 6 Main Branches or ‘Arms’

    Paddington, Slough, Wendover & Aylesbury, Northampton, Saltiford.

Route Overview

Leaving central Birmingham, the Grand Union heads south towards the popular towns of Warwick and Royal Leamington Spa.

Then on to Braunston and Stoke Bruerne, passing through the Blisworth Tunnel, and winding with narrow locks on to the Vale of Aylesbury after passing through the popular market towns of Leighton Buzzard and Tring.
Through the Chiltern Hills, the Grand Union Canal climbs through Berkhamsted, Apsley and Kings Langley on towards Watford. The canal passes under the M25, skirts to the west of Watford, avoiding the town centre, on to Rickmansworth.

From there it runs through the Colne Valley Regional Park, almost following the line of the M25, on through Uxbridge and Cowley, before heading east (just north of the M40) close to the Regents Canal, through Bull’s Bridge eventually to Brentford, where the Grand Union meets the River Thames.

You can find out more about our cruise guides and waterways maps on our canal boat holiday base information pages canal boat holidays in Oxfordshire and canal boat holidays in Warwickshire. 


Feats of Engineering on the Grand Union

The Hatton Flight

The 21 locks in the Hatton flight are nicknamed ‘the stairway to heaven’, a reference made to when workers had to make their way to the top in order to get paid!  These locks and the rest of the main line of the Grand Union Canal was part of a last gasp effort, backed by the government of the day, to modernise the canals so they could compete with road and rail. It took two years and 1000 men to rebuild the 21 Hatton locks alone, using the new material, concrete.

Foxton Locks

Located on the Grand Union Canal in Leicestershire, these locks comprise of two staircases with 5 locks each. Built in 1810, these locks are a spectacular feat of engineering and carry a Grade II listing. They raise boats up to 75ft in approximately 45 minutes.

Foxton Inclined Plane

Foxton is the site of a steam powered ‘Inclined Plane’, an idea to replace the ten existing locks and lift narrowboats 75 feet. It was opened in 1900 but suffered from mechanical and structural problems and the locks were reopened in 1908. You won’t find this on canal maps now, although you can see the remains of the Plane as you ascent / descent the locks along the side.

Watford Locks

The 7 narrow beam Watford locks lift the Grand Union Leicester Arm 16 metres  to the Leicester summit level. They were opened in 1814 and there have been schemes to widen them from 7 foot to 14 foot ever since. They, with Foxton Locks at the other end of the summit level, are the main barriers preventing wide beam boats and barges reaching the waterways of the midlands and north.

Blisworth Tunnel

Opening in 1805, Blisworth Tunnel in Northamptonshire is the third-longest navigable canal tunnel on the UK canal network after Standedge Tunnel and Dudley Tunnel (and the ninth-longest canal tunnel in the world) at 3,076 yards (2,813m) long. At its deepest point it is ca.143 feet (ca.43m) below ground level.

The Iron Trunk

At Cosgrove on the borders between Buckinghamshire and Northamptonshire,  the Grand Union Canal crosses the River Great Ouse via an aqueduct. This cast iron trough, known as the ‘Iron Trunk’ was built in 1811, to replace a previous brick structure that had failed. The structure has two cast iron trough spans, with a single central masonry pier. The trough is 15 feet (4.6 m) wide, 6 ft 6 in (1.98 m) deep, with a total length of 101 feet (31 m). The canal surface is about 40 feet (12 m) above the surface of the river. There are large approach earthworks about 36 feet (11 m) high above the valley floor and 150 feet (46 m) wide, with a total length of half a mile (800m).

Hanwell Flight

Connecting the River Brent to the rest of our canal system, today, Hanwell’s flight of seven locks is located in West London. This flight of seven locks is located next to St Bernard’s Hospital and has features such as lock keeper’s cottages and a ramp to help horses out of the canal when they fell in.

The ‘Arms’ and ‘Branches’ of the Grand Union

The Grand Union Canal which starts in the centre of Birmingham and provides a continuous route to West London also has a variety of Canal Arms and Branches.

Branches added:

  • Wendover arm (1799)
  • Paddington (1801)
  • Buckingham (1801)
  • Northampton arm (1815)
  • Aylesbury (1815) The canal to Newport Pagnell (opened 1817) was built by a separate company
  • Slough Branch was one of the last canals to be built (1882)
Hatton Locks a Flight of 21 Locks on the Grand

The Leicester Section

The Leicester section branches north at Braunston and climbs a little less steeply before falling to join the River Soar just after Loughborough. The canal section before Leicester is very rural at times and has two tunnels at Crick and Husband’s Bosworth and staircase locks at Watford and Foxton. It includes the Market Harborough arm which is very popular for canal runs and canal walks.

Norton Junction

Norton Junction is a major waterways place at the junction of the Grand Union Canal (Leicester Section – Old Grand Union) with the Grand Union Canal (Grand Junction Canal – Main Line – Braunston to Norton) and the Grand Union Canal (Grand Junction Canal – Main Line – Norton to Gayton).

Did You Know?

  • Let’s do business!

    The original Grand Junction Canal was built to link London with the rest of the UK’s canal system. It was a key part of communication and the transport of goods from the industrial north and Midlands to the south and the capital. It received its Act in 1793 and was fully opened in 1805.

  • A bit of the Oxford Canal...

    A five/mile (eight-km) section of the Oxford Canal forms the main line of the Grand Union between Braunston and Napton. Although the Grand Union intended to buy the Oxford Canal and Coventry Canal, these purchases did not take place.

  • Who Owns the Grand Union?

    The Grand Union Canal was nationalised in 1948, control transferring to the British Transport Commission, and in 1962 to the British Waterways Board, later British Waterways and most recently, the Canal and River Trust.

  • What was the main use?

    Original designed for commercial goods traffic, this pretty much ended in the 1970s, though lime juice was carried from Brentford to Boxmoor until 1981. Leisure traffic then took over, with canal boats and canoe clubs as well as fishing and walking.

  • Canal disasters

    Work on the Bilwsorth Tunnel on the Grand Union canal in Northamptonshire began in 1793, but errors led to part of the tunnel collapsing claiming the lives of 14 men. It was then decided to begin again with a new tunnel.

  • Legging It

    Until the 1870s travel through the tunnel was only achieved by men lying on their backs pushing the boats with their feet (legging). From 1871 steam tugs were used to pull boats through, and extra ventilation shafts were installed.

  • Water supply problems

    The canal had water supply problems, especially for the summit between Marsworth and Tring. A navigable feeder was made to Wendover (1797) and several reservoirs with pumping engines built near the junction. Over the years, back-pumping was introduced at many of the locks.

  • North and South

    Interestingly the bridge and lock numbering system restarts at Braunston (where the canal meets the beautiful Oxford Canal), so the Grand Union Canal has a sort of north and south concept.

  • Broad or narrow?

    Although the Grand Junction was built as a broad canal and could take boats 14ft wide, at its northern end it joined the narrow Oxford Canal and the canals which continued the line to Birmingham were also narrow. In practice, therefore, it was generally used only by narrow boats, except at the London end.

Black Prince Autumn - friends going through lock
Black Prince teamwork - friends mooring up

Black Prince Cruising Routes

You can cruise on the Grand Union Canal starting from our bases at Napton in Warwickshire and Stoke Prior in Worcestershire. Check out our canal maps and cruise guides on our base page for waterways guides and more information for your canal holiday.

Napton Canal Hire Base – a cruise guide

From our base at Napton in Warwickshire you can start your canal boat holiday on the Grand Union South, a return trip to Leighton Buzzard and back over a week. This is a real countryside cruise taking you south through pretty scenery to Stoke Bruerne, home of the Waterways Museum, a pretty pub, cafe and ice-cream parlour! Continue south over the River Ouse Aquaduct to Leighton Buzzard before turning and returning home. A longer cruise will enable you to continue to Tring, Berkhamsted and Kings Langley.

Caldon canal to Leek

Black Prince Canal Guides

Below are links to a few of our other canal specific guides and canal maps to help inspire you on your next canal holiday: