Submarine (C5)

THE British naval establishment was not keen to introduce submarines a century ago. Controller of the navy, Admiral Sir Arthur Wilson, thought them"underhand, unfair and damned un-English". It just wasn't cricket, old chap, to sneak up on the enemy like that. Once other major powers started building them, the old guard changed their tune and Britain's first submarine was launched in 1901.

No Occupation For A Gentleman, the first of a two-part documentary about this underwater 'invisible army', did nothing to soothe the nerves of those claustrophobic souls for whom going down in a submarine has as much appeal as being locked in a small dark room. Commanders and seamen confirmed conditions were bad. If you stayed down too long in the early days, the air became foul and it was difficult to breath. When one submarine surfaced after nine hours below, the air expelled when the hatch opened was coloured green.

They weren't the safest means of transport. Early submarines were powered by an electric motor, but propelled by a petrol engine on the surface. This sometimes leaked carbon monoxide, leaving the crew at constant risk of poisoning. Their only protection were three white mice who would squeak and die if the air quality became dangerous. It was a relief to learn that today's submarines generate their own oxygen.

Wilson called submarines no better than pirates, causing the crew to raise the Jolly Roger after the first successful sinking. But they proved their worth time and again in the two world wars.

A third of potential captains failed the seven month training course. It was an unusual command as he was very much his own boss, making his own decisions and taking full responsibility for the men and the submarine. Complex technology in today's nuclear submarines has changed that. The captain is less of a one-man band and more of a team leader - one with a £400m vessel and a cast of around 120.

Perhaps the most usual cargo was a dead body packed in dry ice in a special container and loaded on a submarine in 1943. The corpse, made to resemble a shot-down airman, was put into the water off Spain. The idea was that false papers, put on the body by British Intelligence, would mislead the Germans about the location of a planned invasion of southern Europe. Amazingly, the plan worked. The submarine's secret delivery changed the course of the war.