In 1950, Tidbury married Anne, daughter of Brigadier H. E. Russell, DSO; she was the niece of Colonel Bill Whitbread, who was the long-serving Chairman of Whitbread & Co. Ltd, the brewers. After being discharged from active service, Tidbury started work for the firm; he trained at their Mackeson brewery in Hythe, Kent, before training in rotation at the company's Head Office in London. The following year, he informally became an assistant director and was formally appointed to the position in 1957. In 1959, he was appointed managing director, a role in which he served until his promotion to chief executive officer in 1974. Three years later, he became the company's Deputy chairman and between 1978 and 1984 he was its chairman, remaining on the board until 1988. He also served as director of Whitbread Investment Co. Plc and Gales Brewery in Horndean. By the 1960s, some larger competitors were beginning to take over and amalgamate with smaller breweries; at first, Whitbread's had provided capital exchanges as part of an "umbrella" to protect smaller brewers from takeovers, and in 1966 Tidbury was appointed Chairman of one such firm, Brickwoods Brewery Ltd., a post he held until 1971. But many of these smaller breweries would eventually be taken over by Whitbread's over the course of the 1960s as competition intensified. This left Whitbread one of the "Big Six" brewing companies in the country, but also prompted a rationalisation of the business structure. As the Times summarised, Tidbury's work at the top-tier of this re-organisation "helped to steer Whitbread through a difficult period for both the company and the industry as a whole". Despite beer and spirit sales decreasing during his Chairmanship, Whitbread increased its sales of soft-drinks, introduced more efficient means of production, formed links with Heineken and supermarkets, bought up hotels and developed the Beefeatergastropub chain. This new management plan saw overall sales increase, but meant 1,800 jobs were cut and several breweries closed, decisions which, according to the Times, were not easy for Tidbury, who as "a member of the old school always adhered to rather paternalistic principles of loyalty... knew his pubs and his people." Tidbury was also involved in his industry's professional associations. He served as President of the Institute of Brewing from 1976 to 1978, and Chairman of the Brewer's Society between 1982 and 1984, after which he was its Vice-President. He was Master of the Brewer's Company in 1988. Other positions included President of the British Institute of Innkeeping and President of the Brewing Research Foundation International from 1993.