On the top of this plain the rivers had laid down beds of gravel, some of which could still be found in the neighbourhood. Look for a well and you would find the gravel. At this period the River Thames had gone straight on from Malden and flowed into the North Sea somewhere near Ipswich. This was Thames 1. Then had come an ice age and the path of the river was frozen. He showed us the map of the Thames Valley and the sharp bend southwards that the river now takes at Malden where the river had been frozen. The Thames had had to cut a new bed. There it flowed for thousands of years, cutting the deep valley through Finchley, to the west of the Great North Road. This was Thames 2.
IS MALDEN CORRECT?
With the next ice age, the Thames was blocked again. Now it began to cut the Thanes 3 Valley which we know today. Muswell Hill, Highgate, Hampstead, were left standing high above the river, but an immense volume of soil had been carried down the river and its away to the North Sea to form the Dogger Bank. The Thames had cut its third valley and perhaps, thousands of years from now, in another ice age, the river would cut a fourth one even further south. Geography could repeat itself.
As the teacher spoke I could see a never ending movement of soil, being built up and then moved on, sorted and resorted like sand castles built between the tides and swept away in the next flood. I watched in my mind the rain pouring on Muswell Hill and running down, cutting away the soil. The water which seeped out at Pages Hill and ran down through the allotments into the culvert under Greenham and the other roads, had cut out the valley. Coppetts Road and Colney Hatch Lane were higher up on either side, safely away from the stream. Further over, small springs started in Coldfall Woods and became the familiar stream through the meadow. These were already cutting the ground away. On the other side of the hill there must be others. A complete hill top being eroded and sliding down into the valley.
Before I went to Tollingon School, part of Coldfall Woods had long been felled to make the school sports ground. I liked to stand there looking towards Barnet and imagine myself on a narrow ridge between the two valleys. Thames 2, which once had held the mighty Thames, now carried the insignificant Dollis Brook, while the Thames had been diverted behind my back to the other side of Muswell Hill, capturing on its way the Wandle, the Falcon, The Ravensbourne, the Tyburn and the Fleet and a dozen other tributaries with romantic names from north and south. I stood in Twyford Avenue with a ghostly Thames 2 in front of me and behind me the modern Thames, waiting perhaps to become a ghost in its turn sometime in the distant future.