Nuclear Detectives

The mysterious death in London of the Russian dissident Alexander Litvinenko was a story which could have come from the pages of a dramatic spy novel. But it actually happened - and has still not been fully explained.

This two-part series examines the work of scientists acting as nuclear detectives seeking to identify and control the spread of radioactive materials.

Part Two: Governments

Nuclear know-how is becoming increasingly available and governments, keen to develop their own nuclear weapons programmes, are investigating nuclear technologies.

Is a new round of proliferation underway?

This second programme investigates public - and not so public - nuclear weapons programmes.