On return to Britain he continued to preach, first as an itinerant evangelist and then as a student for the ministry of the United Free Church of Scotland.
[4] As a student at Glasgow University 'DP' (as he was often known, "never with disrespect if not always with affection")[5] created the Glasgow Students Evangelistic Union and led many campaigns, 1922–28, being responsible[6] for encouraging Eric Liddell, the Scottish international rugby player and Olympic gold-medalist athlete, to speak publicly of his faith in Christ.
[14] Thomson edited and/or wrote a substantial number of books and pamphlets on evangelism and on Scottish church history.
[15] Thomson's three autobiographical works were: The Road to Dunfermline: The Story of a Thirty-Five Years' Quest,[16] Why I Believe[17] and Personal Encounters.
In 1934 he was appointed to the staff of the Home Board of the Church of Scotland as an evangelist, leading Seaside Missions in the summer and local campaigns in the winter months.
[34] To support the Fund, 'DP' wrote a short biographical pamphlet: Eric Liddell: The Making Of An Athlete And The Training Of A Missionary, which was published in Glasgow by the Committee in 1946.
[38] From January 1946 'DP' was again appointed by the Home Board as organiser for seaside mission and summer camp work, a post which also allowed him to lead evangelistic campaigns.
Tom Allan, caught public attention for its use of intensive visiting of the parish by congregational members and volunteers from outside.
[41] In order to concentrate on this work, he secured Tom Allan's secondment from North Kelvinside to organize the seaside mission programme of 1949.
Thomson had a supporting role in the Tell Scotland Movement[43] and also in the Edinburgh events of the Billy Graham All-Scotland Campaign of spring 1955.
[44] To coordinate the volunteers Thomson recruited from congregations across Scotland he founded the Work & Witness Movement[45] and, 1955–58, led geographically ambitious campaigns in the Western and Northern Islands.
"[58] Although after 1947 Thomson sought primarily to utilize the "sleeping giant of the lay forces of the Church",[59] his ministry was also said to be responsible for "a steady stream of men and women for the whole-time service of the Church, as ministers, missionaries, deaconesses, lay missionaries and teachers".
[64] After 1955 'DP' diverged from both Tom Allan and Billy Graham, preferring to emphasize the significance of the personal approach rather than the mass meeting as means of outreach, publishing his findings in Dr Billy Graham And The Pattern Of Modern Evangelism, Crieff: St Ninian's Training Centre 1966.
[65] Thomson's influence in the Scottish Churches of the period following the Second World War has been compared to that of Rev.
[68] Thomson & Cowan, Glasgow Marshall, Morgan & Scott, London The Lassodie Press, Dunfermline Cambuslang: Trinity Church of Scotland For The Eric Liddell Memorial Committee For the Melrose Presbytery Campaign Fund The George Wishart Quarter-Centenary Committee Pickering & Inglis, London & Glasgow As Organiser for Evangelism, The Home Board of the Church of Scotland Associated with The Tell Scotland Movement St Ninian's Training Centre, Crieff The Research Unit, Crieff Rebindings