A young Norfolk telephone engineer, Roy Robinson, who has died aged 90 at his Norwich home, helped to build the world's first electronic computer.

Posted to the code-breaking centre, Bletchley Park in Buckinghamshire, after the outbreak of the second world war, he became a key part of the team working with Colossus, which helped to decipher German radio traffic.

After volunteering to join the armed forces, his application was refused and he was summoned for interview by senior Home Office officials.

He was selected for a secret project and became one of the first sent to work on code breaking. It was the success of the Enigma code machines, which helped to shorten the length of the war by as much as two years.

He remained there until 1946 when the equipment was dismantled on the prime minister's instructions. Sworn to official secrecy, it was years after the war that he even told his wife.

Born in Great Yarmouth, Roy Arthur Robinson started work for the Post Office at the manual exchange in Guildhall Hill, Norwich, in 1939, as an engineering apprentice. He had continued to study and gained an engineering degree at the University of London and further engineering, electrical and managerial diplomas and qualifications.

He spent four years at Post Office headquarters, four at regional headquarters and three years from 1970 as deputy general manager at Cambridge. Throughout his 43 years with the GPO, he spent more than half his career in the Norwich Telephone Area.

Responsible for laying the foundations that enabled the progressive expansion of the telephone service in the Norfolk area, he was head of engineering, planning and works. In October 1973, he was promoted as general manager of the Norwich Telephone Area, which had an annual income of �9m, a total of staff of 1,500 and more than 100,000 customers. His area was extended the following year to include the Diss exchanges before he retired from what became British Telecom at 61.

His other interests included Rotary and Scouting and later travel. He was also president of the Association of Retired Telephone Engineers.

He was married for more than 60 years to Norah, who died in 2006. He leaves three sons, David, John and Tim, nine grandchildren and 12 great grandchildren.

A funeral service was being held today at St Mary's Church, Hellesdon, at 9.30am followed by cremation at St Faith's at 11am.

Michael Pollitt