This documentary explores the sinking of the Britannic during the First World War, examining how she ultimately came to suffer the same fate as her sister ship, the Titanic.

Titanic had a twin sister, Britannic, which despite being bigger and better built, sank to the bottom three times faster than the Titanic.

With the outbreak of WW1 the Britannic was transformed from the largest ocean liner in the world to the greatest hospital ship in the world – and yet she is virtually unknown today. Why she sunk so suddenly has remained a mystery for 100 years.

Presenters Kate Humble and Andy Torbet go in search of what caused the demise of the Britannic. While Andy dives to the deadly wreck to find physical evidence Kate speaks to descendants of those aboard and actors bring alive the dramatic eyewitness testimony of survivors.