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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 River Brent rises in Barnet and flows southwards to meet the River Thames at Brentford, a distance of 17 miles. The lower part of the river, from Hanwell is part of the Grand Union Canal.
Wikipedia: Link