The Thames Valley is one of the most significant regions in British Pleistocene geology. This is because the valley, together with its extensions into the south Midlands, central Hertfordshire and offshore, contains the longest and potentially the most complete sequence of Pleistocene sediments outside East Anglia. Of crucial additional importance is the position of the valley marginal to the areas that were overridden by glaciers during the cold stages of the Pleistocene. This position enables the Thames deposits to be linked to those of at least two major glaciations. The deposits preserved in the London Basin record a sequence from the marine transgressions of the Pliocene, through initiation and development of the Thames drainage system, to the diversion of the river in the Middle Pleistocene and its subsequent evolution to the present day.

Within the Thames system, the Lower Thames Valley is a classical area since it includes a number of famous fossiliferous and archaeologically important localities in the terrace deposits. For the purposes of this work the area is defined as extending from central London, where the area adjoins the Middle Thames Valley, to the meridian through Stanford-le-Hope, east of Mucking (Fig. 1). This area includes a sequence of terrace surfaces and underlying deposits associated with the present and former courses of the river and its tributaries.

Since initial recognition of the terrace surfaces, a series of investigators have attempted, using various criteria, to separate and identify the different components of the succession.