In 1912 Clapham joined the Royal Commission on Historical Monuments (England) where he was successively Editor, Secretary, and Commissioner. In 1921 he published a major survey in the
Antiquaries Journal on the
Holy Sepulchre in Jerusalem – the result of his military service in Egypt and Palestine with the
Royal Sussex Regiment during the First World War. His principal work was with the Royal Commission, being a significant contributor to the reports on Essex, Buckinghamshire, Huntingdonshire, Middlesex, London, Hertfordshire, Westmorland, and Oxford. His major achievement was a two-volume work on
Romanesque Architecture in England in 1930 and 1934, and subsequently on
Romanesque Architecture in Western Europe in 1936. He was a faithful adherent of the
Society of Antiquaries, being first Secretary and then its president and later the gold medallist. Although he had never been to university, in 1935 he was elected a
Fellow of the British Academy. Clapham wrote three guide books for the
Ministry of Works, all of which were published posthumously. These were on the Augustinian Abbey at Thornton in Lincolnshire (1951); the Benedictine Abbey at Whitby (1952); St Augustine's Abbey at Canterbury (1955). ==References==