On the night of Friday 13th October 1939, HMS Royal Oak, a 600 foot long 29,000 ton battleship, sank in highly controversial circumstances in the Royal Navy's main anchorage at Scapa Flow in the islands of Orkney. 833 men lost their lives. The 2nd World War is just six weeks old but it rocks the British naval establishment to its core. Sabotage is suspected, but further investigation reveals the shocking news - a German U-boat, U-47, has penetrated the hitherto impregnable natural harbor and sunk the mighty battleship. To this day the wreck remains a monument to a huge sacrifice. Many of her crew were the youngest sailors in the Navy. Her status in the pantheon of Royal Navy ships is assured and she has iconic status. But now she poses an entirely different threat to the northern islands of Britain and once again she is at the center of a new controversy. Her fuel tanks contain thousands of gallons of heavy oil and now this oil is finding its way to the surface. Royal Navy salvage teams are undertaking the difficult job of tapping this oil and removing it. But when she sank, the Royal Oak was stocked with ammunition. It has now been found that this unexploded ordnance is becoming unstable and could explode at the slightest movement. Working alongside scientists, the Royal Navy has developed some of the best survey technology in the world giving perfect 3D dimensional images of the wreck. Gaining unparalleled access, this program is the first to visit the Royal Oak in decades. High quality re-enactments, interviews with survivors and witnesses and heart rending accounts by still grieving relatives take the viewer back to what is still the biggest naval disaster in British history, celebrating its 70th anniversary in October 2009.