We look at erratics on the Pennines. The presenter, Eliot Brown, explains how scientists first realised that ice once covered Britain.

01.55 — 02.30

Aerial shots of present-day Iceland suggest what large areas of Britain must have looked like during the last ice age..

02.30 — 05.55

How ice is formed in sheltered upland hollows; and how its build-up can lead to dramatic erosion of the landscape.

05.55 — 07.50

The impressive glacial trough at Bealach na Baa in north-west Scotland is examined closely.

07.50 — 10.00

The camera surveys some other glacially produced landforms.

10.00 — 11.41

The effects of glacial erosion played a role in the planning of the railway to Kyle of Lochalsh.

11.41 — 16.40

Footage of Iceland leads into a discussion of lowland glaciation, and the importance of outwash by meltwater and the transportation of finer sediments by wind.

16.40 — 17.57

Using maps and a visit to a Shropshire sand and gravel quarry, the presenter shows just how varied and extensive the ice coverage was, and points out the different directions of ice flow and outwash.

17.57 — 18.55

The programme revisits the Scottish Highlands to consider the possibility of ice returning to Britain.