He returned to teach and read for a doctorate at Magdalene College, Cambridge; his thesis, On problems of the British export trade, later had some influence on the reporting of balance of payments figures.

[2] He met and married Valerie Bell during this period, and to finance his PhD studies, in 1952 he joined the British Market Research Bureau (BMRB).

Innovations during this period included the TV Attention Survey (a prototype of modern TV audience research which gave useful insights, enabled JWT to buy airtime better and became a remarkable new business tool) and the creative workshop, which tested new and experimental ideas with qualitative research.

[1] Treasure became a director of the J Walter Thompson company worldwide, becoming vice chairman in 1974, and was president of both the Institute of Practitioners in Advertising and the Market Research Society.

[2] He returned to the commercial advertising world in 1980, running his own agency John Treasure and Partners, which then merged with Freeman Mathews Milne to become Freeman Mathews Treasure, before the Saatchi brothers, possibly in recognition of the role he had played in suggesting them to Margaret Thatcher for the Conservative Party account, invited him to become vice-chairman of their rapidly growing agency.

Colleague and industry commentator Jeremy Bullmore wrote: "Although he retained a certain reserve all his life, Treasure was always possessed of presence; he commanded attention.

The source of this authority was a clear and analytical mind, combined with an enviable ability to express complicated thoughts in jargon-free language.... Treasure's intellectual curiosity, his withering contempt for flabby thinking and his fascination with theory had a liberating effect on others.

He took up the game at the age of 50, becoming an active member of Royal Mid-Surrey Golf Club – and within five years, with RMS professional David Talbot, he had become good enough to compete in the State Express 555 National Pro-Am Championship at Penina in Portugal.