A series of buried valleys situated south of the submerged Chalk outcrop of the Strait of Dover and eroded down to -170 m N.G.F. are recognized as infilled tunnel-valleys excavated subglacially during the Warthe Phase of the Saalian glaciation beneath an ice sheet that advanced up the English Channel from the west. Before the Saalian a Chalk ridge joined England and France. Later in the Warthe, ice withdrew from the English Channel and an ice lobe from the North Sea overrode the Chalk ridge to extend some distance down-Channel, eroding some deep NNE-SSW hollows associated with the tunnel-valleys and scouring out the present deep-water channel; this being probably the first physical opening of the Strait of Dover. The tunnel-valleys were infilled during the Eemian interglacial and finally during the Brorup interstadial as evidenced by palynological study of borehole V 050 cores.