On 13 October 1939, HMS Royal Oak, one of the Royal Navy's top battleships, was sunk at the British fleet's main anchorage at Scapa Flow, Orkney. The audacious attack, by a German U-boat, was the first major blow against Britain of the Second World War. Over 800 lives were lost, including sailors as young as fourteen. Told through declassified photographs and naval records, as well as statements from survivors and the author's personal connection with the tragedy, this is a dramatic and moving reassessment of one of the most shattering events in British naval history.