Seventy years ago, off the Greek island of Kefalonia, the British submarine HMS Perseus hit an Italian mine, sparking one of the greatest and most controversial survival stories of World War II.

The clear waters of the Mediterranean were a death trap for British submarines in World War II.

Some were bombed from the air, others hunted with sonar and depth charges, and many, perhaps most, collided with mines.

Two fifths of the subs that ventured into the Mediterranean were sunk and when a submarine sank it became a communal coffin - everyone on board died. That was the rule.

In fact, during the whole of the war there were only four escapes from stricken British submarines. And the most remarkable of these took place on 6 December 1941, when HMS Perseus plummeted to the seabed ...

This equipment had only been tested to a depth of 100ft (30m). The depth gauge showed just over 270ft, and as far as Capes knew, no-one had ever made an escape from such a depth ...

It's all Greek to me.