Political mendacity – especially in wartime – did not begin with Tony Blair. Churchill himself was honest enough to admit: 'Truth is so precious that sometimes it has to be protected by a bodyguard of lies.’ One awful occasion when the great man deployed that bodyguard in force is the subject of this excellent and moving investigation by journalist-turned-historian Jonathan Fenby.

The 16,000-ton Lancastria was an ageing but still serviceable Cunard liner. Called away from her usual duties of ferrying well-heeled honeymooners and retired Americans round the fleshpots of the Caribbean in 1939 by the sterner demands of war, she was rapidly converted into a troopship. On 17 June 1940, packed