In 1947, after his wartime military service, Trevelyan was appointed Warden and Principal of Attingham Park, an adult training college in Shropshire, where he carried out his pioneering work in the teaching of spiritual knowledge as adult education. The courses ranged from chamber music and drama onto esoteric subjects such as 'Finding the Inner Teacher' and 'Holistic Vision'. The latter attracting large numbers of participants, many of them from other countries as well as Britain. The college was jointly sponsored by the local authority and the University of Birmingham, both of whom looked askance at Trevelyan's attraction towards the mystical; and so it took immense moral courage, for instance, for him to present a course on 'Death and Becoming', a subject that was in those days virtually taboo.