As a pupil at Dunfermline High School, Liddell studied chemistry, mathematics, physics, English and two other languages. He became a reluctant rugby player, under the guidance of retired Welsh international Ronnie Boon, while playing football for local teams and Scotland Schoolboys. By the age of 16, Liddell had progressed sufficiently to earn a contract with Lochgelly Violet football club and be sought after by Liverpool, Hamilton Academical, and Partick Thistle. Liverpool manager George Kay became interested in signing Liddell on the recommendation of the club's Scottish halfback Matt Busby, who learned of the teenager from Manchester City's Alex Herd while on a golf trip. Herd had forwent one of their rounds to take Willie McAndrew, manager of Hamilton, to watch Liddell play for Lochgelly. When Busby queried him about his absence and Liddell, Herd told him that a contract had not been agreed because limited resources prevented Hamilton from offering Liddell the assurances his parents insisted upon. Instead, Liddell signed for Liverpool as an amateur on 27 July 1938 and became a professional in 1939 on a weekly wage of £3. Negotiations between his parents and the club guaranteed, as a pre-requisite to acceptance, that Liverpool would permit Liddell to continue his accountancy studies, be housed in suitable accommodation, and be employed part-time an accountant at a company in the club's city.