Between the entry of the US and the end of the Second World War in Europe, the three huge Cunard liners Aquitania, Queen Mary and Queen Elizabeth carried a million GIs and British Empire troops across the North Atlantic at up to 16,000 men per voyage - without either naval or air escort. What became known as the 'Shuttle Service' was a great gamble, but it was considered a risk worth taking since it was the only way so many men could be transported to the theatre of war so quickly: indeed, Churchill reckoned they shortened the war by a whole year. The ships themselves were very fast, and were armed for self-defence, but to avoid potential U-boat traps they relied heavily on intelligence, now known to be the product of 'Ultra' (decoded Enigma traffic). The author, as a young Australian naval reservist, served as a cipher officer on these ships, so was at the centre of this work. Although he was not supposed to, he kept a private journal, and his attendance at sailing conferences allowed him to record details that would otherwise have been lost.

His book combines a personal account of these years, with a knowledgeable analysis of how this feat was organised, both ashore and aboard the ships themselves. Conditions were so tight that soldiers slept in shifts (the original 'hot bunking'), while so much water was consumed that the ships became dangerously unstable as the double-bottom tanks were emptied during the voyage. By way of contrast with the testing environment afloat, the author also provides some entertaining observations of life in wartime London and New York.