It was a huge challenge. Not only had much of the work never been done before, but as Mary would point out, she was working on a notoriously unreliable valve computer, but also one that had just 2K bytes of computer storage compared to the “umpteen gigabytes” available to present programmers.

“When it was LEO 1, you had to know a lot about the machine itself because there was so little storage space that every instruction had to be essential, or it had to be knocked out,” she would recall.

As well as working on programming to handle payroll for companies such as Ford Motor and Lyons itself, Mary became involved in such jobs as tax tables for the Inland Revenue, Met Office work and the calculation of ballistics for the Army. She went on to become a supervisor and worked to locate and repair coding errors in the programs created by others.

Family commitments meant that she ceased full-time programming in 1964, but continued to work part-time editing computer manuals and for a few months ran a computer programming course for severely disabled residents at the Princess Marina Centre, Seer Green, sponsored jointly by ICL and Buckinghamshire County Council.

It was not until late 1969 that she ended her formal connection with the LEO team.