River Brent

The River Brent rises on the high ground of Bushey Heath in the London Borough of Barnet and flows south-west for 17.9 miles before joining the Thames at Brentford. Its name appears in a letter from the Bishop of London in 705 as Breġuntford, linked to the Celtic word for ‘high’. The river’s course crosses three distinct zones: a flat southern plain below 40 metres, a basin ringed by hills in the north-west, and steep-sided valleys in the north-east. These valleys include those of Dollis Brook, Folly Brook and Mutton Brook, which cut through older layers of London Clay. The oldest geological layer, London Clay, is over 100 metres thick in places and underlies much of the catchment. The Brent is a young river, formed only about 450,000 years ago during the Anglian glaciation. Before that, an ancestral Thames flowed north-east past Watford, receiving tributaries from the south. One of these tributaries, the proto-Mole-Wey, ran in the opposite direction to today’s Brent, carrying chert from the Weald across what is now the Brent catchment. Gravel deposits from this ancient river, known as Dollis Hill Gravel, rest at heights of around 100 metres near Muswell Hill. These deposits show that the valley now occupied by the Brent existed as a low-lying area over a million years ago. Visitors can follow the Brent’s course through quiet green spaces and wooded valleys. Horsenden Hill and Barn Hill rise above the basin, offering views across the catchment. The steep-sided valleys of Dollis Brook and Mutton Brook provide shaded walks among older trees. Near Brentford, the river meets the Thames at a broad, slow-moving junction. The contrast between the flat southern plain and the hilly north-western basin shows how the landscape has changed over centuries. The Brent’s quiet presence today contrasts with its dramatic geological past.