Turkey Brook

It rises in Potters Bar, Hertfordshire, and flows broadly eastwards to merge with the River Lea Navigation near Enfield Lock.

[1] The brook rises near the Fir and Pond Woods nature reserve in Potters Bar, and at first flows in an easterly direction.

[5][6] As a west bank tributary of the lower River Lea, Turkey Brook came into being about 400,000 years ago, after the Anglian glaciation.

Until the Anglian glaciation, the River Thames flowed north-eastwards via Watford, through what is now the Vale of St Albans, then eastwards towards Chelmsford and the North Sea.

[7] Prior to the Anglian glaciation, a "proto-Mole-Wey" river was flowing northwards from the Weald and North Downs, through the "Finchley depression" and Palmers Green, to join the proto-Thames somewhere around Hoddesdon, at what is today an altitude of around 60 metres.

It flowed into the newly diverted Thames, which at that time was spread over a wide flood plain extending as far north as Islington.

They, and their own tributaries, cut down successively through till left by the ice sheet, then through "Dollis Hill Gravel", and then into London Clay below.

During the course of the following 400,000 years, the lower Lea moved steadily eastwards, leaving river terrace deposits of decreasing age and altitude as it did so.

The Lea and the two brooks cut down into the London Clay (to a today's altitude of c35m), thus defining the north, east and south sides of what was becoming Forty Hill.

But, in Enfield, the engineers who constructed it took the New River on a loop going west, to the north of Forty Hill, and then across Cuffley Brook near Flash Lane (and, later, across an aqueduct[14] there).

From that point, they took it south-east, through the water gap at Beggars Hollow, along the dry channel north of Clay Hill, and down to where Ladysmith Road is today.