Britain first becomes an island about three hundred and fifty thousand years ago, near the beginning of the Wolstonian stage, named after the site of Wolston in the English county of Warwickshire where corresponding deposits were first identified.

This period sees the introduction of Levallois flint tools, possibly by humans arriving from Africa, although finds from Swanscombe and Botany Pit in Purfleet support Levallois technology as a European rather than African introduction.

This more advanced flint technology, which made hunting more efficient, therefore made Britain a more worthwhile place to remain until the increasingly cool climate of the Wolstonian Stage, which apparently includes three periods of glaciation, made continued habitation unattractive, if not impossible.

Acheulean flint tools, typically found with Homo erectus remains, have been found in Wolstonian deposits.

...Swanscombe.

The Swanscombe fossil from southern England, the skull of an adult female with heavy brow ridges and a large projecting face.

Identified as Homo heidelbergensis, the Swanscombe skull dates to the Hoxnian Interglacial of four hundred thousand years ago, and since this follows the extreme Anglian ice age which drove humans out of the British Isles, the Swanscombe people must represent a re-colonization.

It is among these and similar finds in Africa that the line of distinction between Homo erectus and Homo sapiens becomes dim, for one species is apparently grading imperceptibly into its successor.