Mavis Batey, who has died aged 92, was one of the leading female codebreakers at Bletchley Park, cracking the Enigma ciphers that led to the Royal Navy’s victory at Matapan in 1941. She was the last of the great Bletchley “break-in” experts, those codebreakers who found their way into new codes and ciphers that had never been broken before. Mavis Batey also played a leading role in the cracking of the extraordinarily complex German secret service, or Abwehr, Enigma. Without that break, the Double Cross deception plan which ensured the success of the D-Day landings could never have gone ahead….
Mavis Lilian Lever was born in Dulwich, south London, on May 5 1921, the daughter of a postal worker and a seamstress. The family always went on holiday to Bournemouth, but after passing her German O Level, Mavis persuaded her parents to take her to the Rhineland. It was this that encouraged her interest in the German Romantic poets. She was reading German at University College, London, when war broke out, and decided to break off her studies and become a nurse; but she was told that the country could make more use of her as a German linguist….
She initially worked in London, checking commercial codes and perusing the personal columns of The Times for coded spy messages. After showing promise, she was plucked out and sent to Bletchley to work in the research unit run by Dilly Knox….
Although only 19, Mavis began working on the updated Italian Naval Enigma machine and, in late March 1941, broke into the system, reading a message which said simply: “Today’s the day minus three.” “Why they had to say that I can’t imagine,” she recalled. “It seems rather daft, but they did. So we worked for three days. It was all the nail-biting stuff of keeping up all night working. One kept thinking: ‘Well, would one be better at it if one had a little sleep or shall we just go on?’ — and it did take nearly all of three days. Then a very, very large message came in.”
The Italians were planning to attack a Royal Navy convoy carrying supplies from Cairo to Greece, and the messages carried full details of the Italian plans for attack: “How many cruisers there were, and how many submarines were to be there and where they were to be at such and such a time, absolutely incredible that they should spell it all out.”
The intelligence was phoned through to the Admiralty and rushed out to Admiral Andrew Cunningham, commander of the Royal Navy’s Mediterranean Fleet. “The marvellous thing about him was that he played it extremely cool,” Mavis said. “He knew that they were going to go out and confront the Italian fleet at Matapan but he did a real Drake on them.”
The Japanese consul in Alexandria was sending the Germans reports on the movement of the Mediterranean Fleet. The consul was a keen golfer, so Cunningham ostentatiously visited the clubhouse with his clubs and an overnight bag. “He pretended he was just going to have the weekend off and made sure the Japanese spy would pass it all back,” Mavis recalled. “Then, under cover of the night, they went out and confronted the Italians.”
In a series of running battles over March 27/28 1941, Cunningham’s ships attacked the Italian vessels, sinking three heavy cruisers and two destroyers. Without radar, the Italians were caught completely by surprise, and 3,000 of their sailors were lost….
Arguably her most important role, however, was in the collaboration with Knox and Margaret Rock on the breaking of the Enigma cipher used by the German secret service, the Abwehr. MI5 and MI6 had captured most of the German spies sent to Britain, and those in the neutral capitals of Lisbon and Madrid, and turned them back against the Germans, feeding them false information designed to deceive them in an operation known as the Double Cross system. But they had no idea whether or not the Germans believed this intelligence, as the Abwehr Enigma was so complex that Hut 6 had been unable to break it. It had four rotors instead of the standard three, and unlike other machines they rotated randomly with no predictable pattern.
Knox took over the task of breaking it, using Mavis Batey and Margaret Rock as his assistants, to test out every possibility. On December 8 1941 Mavis Batey broke a message on the link between Belgrade and Berlin, allowing the reconstruction of one of the rotors. Within days Knox and his team had broken into the Abwehr Enigma, and shortly afterwards Mavis broke a second Abwehr machine, the GGG, adding to the British ability to read the high-level Abwehr messages and confirm that the Germans did believe the phoney Double-Cross intelligence they were being fed by the double agents.
This allowed the XX Committee, which was running the double agents, to send a stream of small pieces of false intelligence that would build up a complete picture of a fictitious First US Army Group, which was forming up in East Anglia and Kent to lead the main Allied invasion force. The false intelligence led the Germans to believe that the main force would land on the Pas de Calais rather than in Normandy. As a result Hitler insisted that two key armoured divisions were held back in the Calais area….
After the war Mavis Batey brought her indefatigability to the protection of Britain’s historical gardens. Her interest began in the late 1960s, when her husband was appointed the “Secretary of the Chest”, the chief financial officer of Oxford University. They lived in a university-owned house on the park at Nuneham Courtenay and she set about ensuring that the overgrown gardens were restored to their original landscaped state. She became the driving force behind moves by the Campaign for the Protection of Rural England, English Heritage and the Garden History Society to protect historical gardens. Working with the Historic Buildings Council, she instigated the formal recording of historic gardens which led to the publication of English Heritage’s Register of Parks and Gardens of Special Historic Interest in England in 1984. She had taken a leading role in the Garden History Society since 1971 when she became its Secretary, and was its president from 1985 until her death.