Philip Lyth began his career as a student and teacher at Swedish Folk High Schools ('Ungdomskolor' - residential colleges for rural and industrial workers), and spent three years working on farms in Sweden. Between 1942 and 1945 he was the first full-time organiser of Young Farmers' Clubs in county Durham. He also worked at the School of Agriculture at Houghall, county Durham, in the 1940s. By 1948 he was working at the Derbyshire Farm Institute at Broomfield Hall, Morley.
He was Principal of the Nottinghamshire College of Agriculture at Brackenhurst near Southwell for 25 years, and established a farm museum there. His book 'Farm Crafts Today' was published in 1962. In his retirement he wrote, lectured and broadcast on various aspects of agricultural heritage, landscape history and nature conservation. He was a Council member of the Thoroton Society of Nottinghamshire, founder and President of the Nottinghamshire Farming and Wildlife Advisory Group (FWAG), and in 1984 was President of the Nottinghamshire Local History Association. For many years he ran courses for the University of Nottingham Adult Education Department/Workers' Educational Association (WEA) relating to the agricultural and landscape history of Nottinghamshire.
The Southwell WEA Local History Group, under Lyth's leadership and editorship, wrote the book 'Farms and Fields of Southwell' (1984, revised 1991). Lyth's own publications included 'The Southwell charter of 956 A.D.: an exploration of its boundaries' (1984), 'Georgian Southwell: as seen in the journals of the George Hodkinsons, Attorneys at Law, 1770-81', with R.E. Hardstaff (1986?), 'A History of Nottinghamshire Farming' (1989), and 'The Saxon charter boundary of 956 A.D. and the mediaeval deer parks of the Archbishops of York at Southwell' (1989).