In 1912 he joined the British Tabulating Machine Company (BTM), established to import and assemble American punched card technology.
It was, however, useful only as long as the Germans continued with particular weaknesses in operating procedure, which they gradually tightened up, so that the Polish success rate diminished dramatically.
Alan Turing designed the British bombe on a more general principle, the assumption of the presence of text, called a crib, that cryptanalysts could predict was likely to be present at a defined point in the message.
As chief engineer at the British Tabulating Machine Company at Letchworth Keen was approached to turn these ideas into a working reality.
The second bombe, named "Agnus dei", later shortened to "Agnes", or "Aggie", was equipped with an important additional feature, the diagonal board that had been designed by Gordon Welchman.