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The Grand Union is a 137 mile (220km), 166 lock, 2 tunnel canal running between Brentford in London and Birmingham. It is the longest canal in Britain, and has 11 main arms and junctions. It takes over a week to navigate.

The Leicester arm branches off at Norton Junction and runs 66 miles long through 59 locks (including 2 staircase locks at Foxton) and 2 tunnels to Leicester where it continues into the River Soar.

Read more at Wikipedia Link

The flight of six locks at Hanwell raises the Grand Union Canal by just over 53 feet above the height of the River Brent over a distance of a third of a mile. Located in a pleasant rural setting, the locks have been designated a Scheduled Ancient Monument by English Heritage.

They are the work of William Jessop, chief engineer of the Grand Junction Canal, who had the foresight to design the locks to be wide enough to accommodate two narrowboats at the same time.

The locks are bounded on the north by the former County Asylum (known as Hanwell Asylum), now Ealing Hospital. The long brick wall between the locks and the hospital is also a Scheduled Ancient Monument. A bricked-up arch can be clearly seen in this wall. This is the site of a short branch of the canal which led to a dock within the asylum. Canal boats used this dock to deliver coal for the Asylum's boilers and to take away fruit and vegetables which were produced in the asylum's large market gardens.

There are some side ponds at the locks. These were used to store reserves of water to keep the locks topped-up as required.

Some lock-keepers cottages survive as private residences, but some have been demolished.