Throughout the 1970s and 80s, the front line of the Cold War was hidden beneath the ocean. Submariners from three navies - American, Soviet and British - played a deadly game of cat and mouse in a secret war of espionage and intimidation. The nuclear balance between East and West was constantly shifting.

For decades, Britain and America's Cold War submarines waged a secret war of espionage against the Soviet navy. Deep in the ocean, crews were locked in a game of cat and mouse as each side battled to gain the tactical and technological advantage.