The battlecruiser HMS Hood was the pride of the Royal Navy for more than 20 years, but when it was sunk by the German battleship Bismarck off the coast of Greenland in May 1941, its end was shockingly swift. This 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, piecing together evidence as to why it sank so quickly