Batey was due to go to Canada for the Fleet Air Arm advanced flying course in late 1942, by which time he was engaged to Mavis Lever, a young female codebreaker who was working with Knox. Batey and Mavis had met when he helped her to solve a complex cipher problem. Mavis later recalled: "I was alone on the evening shift in the Cottage and this time I sought the help of what Dilly called 'one of the clever Cambridge mathematicians in Hut 6'; as luck would have it, it was Keith Batey. We put our heads together and in the calmer light of logic and much ersatz coffee solved the problem. Perhaps Welchman had a point when he said that 'the work did not really need mathematics but mathematicians tended to be good at it'. Dilly made no objections to my having sought such help and even took it in his stride when, after a decent interval, I told him I was going to marry the said 'clever mathematician from Hut 6'. He gave us a lovely wedding present."