The computer was developed from Second World War radar work done at the Telecommunications Research Establishment (TRE) at Malvern, Worcestershire, where Tootill was involved in installing and trouble-shooting airborne radar systems.

After the war, Frederic Calland Williams, was appointed to the chair of electrotechnics at Manchester University, and he bought in Tootill to work on a computer memory project.

To test the memory when it was constructed, Tom Kilburn and Tootill designed an elementary computer, officially known as the Small-Scale Experimental Machine, but better known as “Baby”. The computer could store just 32 instructions or numbers using a single cathode ray tube. The machine first worked in June 1948, taking 52 minutes to find the highest factor of 2, involving about 3.5 million arithmetic operations.

The following year, Tootill transferred to Ferranti, the Manchester-based electrical engineering company, to specify a full-scale computer based on the Manchester University ideas. The first Ferranti Mark I, the world’s first commercially available computer, was delivered to the university in 1951.

When Ferranti failed to pay him enough, Tootill took up a senior lectureship at the Military College of Science, Shrivenham, near Oxford. Then he joined Stuart Hollingdale, head of the mathematics division at the Royal Aircraft Establishment, Farnborough, Hampshire and collaborated on a book called Electronic Computers (1965), aimed at the layperson.

From 1963 to 1969, Tootill was seconded to the European Space Research Organisation, where he established a network of computerised ground stations. In 1973 he transferred to the National Physical Laboratory to work on the European Informatics Network. This was an experimental computer network that established technologies now used in the internet.

He is survived by Joyce, three sons, Peter, Colin and Steven, from his first marriage, and two grandchildren, Mia and Duncan.