How Nelson's heir neutralised a French fleet by writing to it

Charged with the task of supporting Britain's only viable battlefront, the Middle East, in the darkest days of 1940, Admiral Andrew Cunningham sent a suitably Nelsonian signal to the Admiralty: "I intend to act offensively!" The parallels with his great predecessor in command of the Mediterranean fleet would not have been lost on Cunningham that summer. He shouldered the awesome responsibility of keeping open the sea lanes to Britain's only effective army, with all European mainland ports closed to him, except in Greece, and his own home ports facing invasion.

Hence the subtitle of this book, which uses documentary sources on the intelligence war - unavailable to Cunningham when he wrote his autobiography in 1951 - to give what will surely be the definitive account of an underrated campaign.

John Winton writes with a clear, professional expertise, as a former submariner as well as an authority on Ultra, and gives fascinating details for the first time of the role of the latter in the battle of Cape Matapan."ABC", as Cunningham was known throughout the fleet, was tipped off by the deciphering centre at Bletchley Park, that the Italians were planning a major strike by their fleet against British convoys supplying Wavell's desert campaign. Cunningham did not share the blimpish service prejudice against the Fleet Air Arm, appreciating the ability it gave him to strike over great distances at a numerically superior enemy.

He had already deployed it with devastating effectiveness against the Italian fleet in harbour at Taranto in March 1941. The naval airmen prevented the annihilation of Cunningham's cruisers, and then torpedoed the Italians' most powerful battleship, allowing ABC to turn the tables and sink three of their cruisers in a spectacular night action at Matapan.

At Christmas 1941 the Italians wreaked their revenge in what Cunningham described as "an act of cold-blooded bravery and enterprise" when six frogmen planted explosive charges on the hulls of his two remaining battleships. There were times, however, when Cunningham felt that his most formidable opponent was the prime minister himself. In July 1940 when Cunningham was in the middle of delicate negotiations with the commander of the French squadron in Alexandria to try to win them over to the Allies,Churchill sent him a telegram demanding "do NOT FAIL!" Had the issue not been so serious, with a reprise of the sinking of the main French fleet at Oran a distinct possibility, the episode would have been pure farce, with boatloads of British seamen rowing round the French ships, displaying blackboards with "See sense - or else!". Cunningham's use of the iron fist in the velvet glove paid off, with the French crews accepting internment by siphoning off their fuel oil. Cunningham's staff officer wrote, "his handling of the French problem was masterly. In disregarding his instructions (to use force) he was truly Nelsonic!" Churchill's "prodding" despatches became an infuriating feature of their communications and elicited an equally robust response from a commander who did not tolerate uninformed interference. From 1942, however, after Cunningham's brilliantly successful strategy in running convoys through the "Bomb Alley" of the Sicilian Narrows, which relieved the siege of Malta and supplied the Allied armies in Africa, Churchill fully recognised the qualities of a fellow fighting spirit - "the gallant Cunningham". After a spell with the Naval Mission in Washington Cunningham returned to the Mediterranean in 1943 in time to oversee the Allied landings in Sicily and at Salerno. He also took the surrender of his old opponents, the Italian fleet, saving them, however, from further indignity by allowing the ships to fly their colours as they entered Malta's Grand Harbour. Appointed First Sea Lord in October, he went on to attend the summit meetings at Cairo, Quebec and Potsdam that decided the final strategy of the war and the postwar division of Europe.

Winton has written a first-rate biography of one of the key figures of the second world war.

John Crossland is a writer specialising in naval history.