Harold Rowdon was born in Sucre, Bolivia on 26th September 1926 to Reginald Robert and Alice Elsie Rowdon, who were Christian Brethren missionaries with links to the missionary organisation Echoes of Service. Reginald Rowden died of Typhoid fever shortly after Harold Rowdon's birth, and the family returned to England soon afterwards. They attended Bargates Gospel Hall, where Rowden experienced a childhood conversion at the age of 5, and was baptised in 1938.
Rowdon attended Bournemouth School and University College in Southampton where he studied Medieval and Modern History and served as president of the Christian Union, graduating in 1953. As a conscientious objector, he worked as a hospital porter and a teacher during the Second World War.
In 1954, Rowdon began work at the London Bible College as a teacher of History and Church History. Soon, Church History was Rowdon's focus, and he played a major role in the development of the London Bible College curriculum. He also served as the tutor responsible for residential life at the college until his retirement in 1991.
Rowdon attained a PhD with a study of Brethren history, which was published under the title: The Origins of the Brethren: 1825-1850, in 1966. He also contributed numerous articles on Brethren history and on world mission to encyclopaedias, journals, and bible commentaries, and published further books in entitled London Bible College: The First 25 Years and Law and Grace in 1968, Turning The World Inside Out in 1982, and Who are the Brethren and does it matter? in 1986.
Rowdon's work at the London Bible College led to his being invited to preach and teach at Brethren assemblies, at churches of other denominations, and at the annual residential Brethren Conferences. He became involved in multiple Brethren and interdenominational faith mission committees, including the Regions Beyond Missionary Union, the Bible and Medical Missionary Fellowship, and the Bloomsbury Committee who organised Bible teaching meetings in central London.
Rowdon was part of the editorial committee for the Brethren magazine Harvester (later renamed Aware), and was a member of the council for Counties Evangelistic Work. In the 1960s he was a founder member of the Christian Brethren Research Fellowship (CBRF, later renamed Partnership), which was part of an initiative created to re-energise Brethren movement. Although initially doubtful of the more radical approach of the CBRF, who proposed to support and resource Brethren assemblies and to encourage the modification of practices in order to allow women to play a more active role, Rowdon later became wholeheartedly involved in its work, assisting in the production of procedures for the employment of full time church workers. Rowdon also edited a quarterly magazine for Partnership, entitled Partnership Perspectives (later International Partnership Perspectives). He was the international secretary of Partnership, and a part of the committee for the International Brethren Conferences, developing and assisting in relationships between Brethren leaders from countries all over the world. Following his retirement, Rowdon continued to write and publish books and booklets on missionary work and Partnership.
Rowdon is credited as one of the first scholars to bring the study of the Christian Brethren into the realms of academia. In his article 'To Equip and Encourage: The Life of Harold H. Rowdon', Ian M. Randall lists his other interests as including cross-country running, walking, cricket and the historiography of Winnie the Pooh.
