Crossing Continents (11.00 am R4). Julian Pettifer in the Basque country.
The Material World (4.30 R4). The mysterious single waves known as solitons, with explanation from Alan Boardman (Salford University) and Chris Eilbeck (Heriot-Watt).
EUtopia: Walk to Work (7.30 BBC Knowledge). The documentary series about various aspects of Europe, eight episodes of which were shown on BBC2 in the summer, is now apparently having its remaining programmes shuffled on to the BBC’s digital channel. (By contrast, in Germany, all 20 were shown on mainstream television.) This programme follows a group of protesters on a march from Brussels to Cologne in May 1999 to put forward the "People’s Demands" for social justice. For an overview of the whole EUtopia series, see the production company’s airing schedule here .
Behind the Wire (8.00 R4). David Cesarani on the wartime internment of "enemy aliens". This second programme concentrates on how the US treated people of Japanese descent after Pearl Harbor.
Extraordinary Ancestors (8.00 C4). Investigating some family histories from Cardiff.
Costing the Earth (9.00 R4). CFC gases and the ozone layer; Chernobyl’s legacy; the greenness of the Olympics. This - the final programme in the current series - updates earlier investigations.
Horizon: The Lost World of Lake Vostok (9.00 BBC2). About the huge lake under the Antarctic ice, and what the British, Russian and US scientists might find there.
The Science of Secrecy (9.00 C4). The decoding of the Zimmermann Telegram in 1917, and the unsung Old Etonian who did it. See the website at www.channel4.co.uk/nextstep for information about the series’ associated puzzles.
Dispatches (9.30 C4). The Search for Lucie Blackman, the Briton who disappeared from a Tokyo night club in July.
Open Science (from 12.30 am BBC2). Beginning with The Next Big Thing: The Reality of Risk , a discussion (co-produced with Harry Kroto’s Vega Science Trust) on questions of safety, from BSE to vaccination.