On 1 June 1939 His Majesty's Submarine Thetis sank in Liverpool Bay while on her diving trials. Her loss is still the worst peacetime submarine disaster the Royal Navy has yet faced when ninety-nine men drowned or slowly suffocated during their last fifty hours of life.The disaster became an international media event, mainly because the trapped souls aboard were so near to being saved after they managed to raise her stern about 18 ft above sea level. Still the Royal Navy-led rescue operation failed to find the submarine for many hours, only to rescue four of all those trapped. Very little is known about what actually happened, as the only comprehensive book written on the subject was published in 1958.Many years have now passed since the Thetis and her men died, for which no one was held to be ultimately accountable. However, a great deal of unpublished information has come to light in archives throughout the United Kingdom and beyond. After four years of painstaking research...