Stephen McGinty is an author, journalist and documentary producer.

In 1973, two British men, Roger Chapman & Roger Mallinson were 1500ft below the surface laying trans-Atlantic telephone cables in the Pisces III submarine.

What happened next is one of the longest, most dangerous, complex and daring rescues ever attempted as America, Canada, Ireland and Britain marshalled their forces in the air and beneath the sea to save the two men, all while their oxygen, food and power was rapidly running out.