It's been 50 years since nuclear submarines first came to Scotland, and more than 40 since Britain's nuclear missile fleet was stationed on the Clyde lochs. But the Trident fleet is ageing, and the decision to start work on its replacement has been delayed until 2016. With public spending under unprecedented pressure, there's a very real debate over whether we can afford the 20 billion-pound bill. Partly filmed on board one of Britain's nuclear bomber submarines, 'Who Needs Trident?' asks whether a Cold War weapon, designed to deter the Soviet Union from attacking Britain and its NATO allies, is still relevant in the 21st century, and whether Britain, and Scotland, gain anything from it being replaced. Presented by Sally Magnusson.