After serving in the Army Education Corps, he worked as assistant district commissioner in Uganda before joining the Cambridge Examinations Board as an administrative officer.
In 1970 he was appointed to the staff of the South Western Examinations Board, one of the regional boards that existed at that time to administer CSE examinations, and was promoted to become secretary to the board in 1979.
He displayed robust powers of leadership by introducing radical reform of the board's system of marking, moderation and grade awarding. His own administrative ability and expertise in the technicalities of assessment were indisputable. He was firmand forceful, yet without being autocratic.
His appetite for hard work - he regularly spent three or four hours in the evenings at his office desk drafting discussion papers - was legendary with the board's staff, as were the miles he clocked up in the line of duty.
In the mid-1980s, the Conservative government announced the introduction of a single system of examining at 16-plus. In 1988, Edmundson was offered the job as the first full-time secretary of the central co-ordinating body representing the collective voice of the new examining groups formed to deliver the new GCSE.
The government was anxious to impose strict regulatory control over the groups - a difficult task that Mr Edmundson had to undertake. The groups were effectively placed in competition with each other but could no longer offer as many distinctive syllabuses as before. He had to exercise all his skills in administration and diplomacy to steer the council towards adopting measures which would be acceptable both to the boards and to the government in its policy of driving up standards.
Mr Edmundson soon made his mark and over the ensuing years a stream of common practices, procedures and systems resulted in every major operational area.
Throughout, he made sure no one lost sight of the young people whose best interests the examining system was designed to serve.
The appointment was offered to him initially for a year, but he was judged so successful in the work that he was confirmed in the post each time the appointment came up for renewal, and he kept it until his retirement in 1995.
He was awarded the OBE in recognition of his services to education.
Mr Edmundson is survived by his wife, Katie, and daughter, Charlotte. A memorial service in his honour was held at St Martin's-within-Ludgate, central London, on June 22.