 While researching and writing, he was also headmaster of Kirkwall Grammar School (then called the Burgh School).He was appointed in 1914 after some years teaching in Lancashire, and continued as headmaster until 1929, when he was made director of the Orkney Education Committee, a post he held until 1946.Dr Marwick was one of the founders of the Orkney Antiquarian Society in 1922 with fellow Orcadian and Norse enthusiast John Mooney JP, FSA (Scot) and was its secretary for 17 years, during which he contributed papers to its "Proceedings".