The 'mighty' Hood was the pride of the British Navy for more than 20 years, revered around the world as the largest and most powerful warship afloat.

But when it was sunk by the German battleship Bismarck off the coast of Greenland on 24 May 1941, its end was shockingly swift.

For decades, no one has been able to discover why the Hood sank so quickly and two official Boards of Inquiry investigated but failed to explain the tragedy.

A Channel 4-funded expedition in 2001 discovered the wreck for the first time but the investigation was largely inconclusive.

Now two of the world's leading shipwreck detectives have returned to crack the puzzle of the Hood's end.

Although Hood opened fire first with her massive 15-inch guns, it was Bismarck who struck the telling blows, hitting Hood at least twice and causing an enormous explosion and fire.

Hood's shattered hull sank in minutes and only three of its crew survived. In the largest loss of life ever suffered in a British warship, 1415 were killed.

The programme follows deep water search and recovery expert David Mearns and marine archaeologist Innes McCartney as they search the wreck with a state-of-the-art remotely operated underwater vehicle (ROV).

Through three dives in perilous conditions they piece together evidence hidden nearly 3km beneath the ocean's surface.

The programme also highlights a recent effort sponsored by Microsoft co-founder and philanthropist Paul G. Allen, who volunteered the use of his expedition yacht, M/Y OCTOPUS, after the Ministry of Defence gave permission to recover the Hood's bell as a memorial to the ship and her crew.

It tells the story of this epic battle, and pays tribute to the men who lost their lives on board.