In 1998 Manchester University and the City of Manchester celebrated the 50th anniversary of one of the scientific breakthroughs that define the modern era – the world’s first electronic stored-program computer. For the occasion, a team of volunteer engineers had built a working replica of that original computer. The replica was inaugurated by Tom Kilburn and Geoff Tootill, its two surviving creators, and is now a permanent exhibit in the Manchester Museum of Science and Industry. Tootill has died aged 95.

The original 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. In another laboratory at TRE, a rising academic star, Frederic Calland Williams, and Kilburn, his assistant, were working on an electronic data storage system intended for use in radar. The system used a conventional cathode ray tube to store the data.

When the war was over, Williams – still only in his mid-30s – was appointed to the chair of electro-technics at Manchester University. By this time computers were in the air, and designing a suitable memory technology was the outstanding technical challenge. He brought in Kilburn and Tootill to work on a computer memory project.

In order to test the memory when it was constructed, 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 2ⁱ⁸, involving about 3.5m 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.

Dissatisfied with his salary at Ferranti, Tootill took up a senior lectureship at the Military College of Science, Shrivenham, near Oxford. The college offered no opportunity for research, so in the mid-1950s he leapt at the offer of a research position from Stuart Hollingdale, head of the mathematics division at the Royal Aircraft Establishment, Farnborough, Hampshire. He and Hollingdale collaborated on Electronic Computers (1965), a book for the layperson. Published as a Pelican Original, it filled a vacuum of information about computers, and sold remarkably well.

From 1963 to 1969 Tootill was seconded to the European Space Research Organisation, where he established a network of computerised ground stations. Returning from this high point in his career, he was assigned a bureaucratic role that he detested.

Relief came in 1973 when 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.

Born in Chadderton, Lancashire, Geoffrey was the only child of Frederick Tootill, a journalist, and his wife, Alice (nee Tetlow), a school teacher before her marriage. He grew up in Birmingham, where his father was Midlands manager for the Co-operative Press. Like many scientifically minded boys of the era, he built radio sets and experimented with electronics. He was educated at King Edward’s high school, Birmingham, where he excelled in the sciences and won a scholarship to Christ’s College, Cambridge University, to read mathematics.

He went there in 1940. Following Britain’s entry into the second world war, the normal three-year degree programme had been compressed into two years. Studies were intense and it was at this point he realised that his vocation did not lie in mathematics. He sat in on some engineering lectures and realised he was “a competent engineer … whereas I was a pedestrian mathematician”.

After graduation he was directed to work of national importance, initially as a mathematician in operations research. However, after a few weeks he managed to switch to an engineering role at the TRE. Outside work duties, he joined the TRE’s Flying Rockets Concert Party, where he met Pamela Watson, a laboratory technician. They married in 1947.

Two years after Pamela’s death in 1979, Tootill married Joyce Turnbull. He retired in 1982 but remained active in computing and academic pursuits.

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

• Geoffrey Colin Tootill, computer engineer and scientific civil servant, born 4 March 1922; died 26 October 2017