During the First World War on 16 December 1914, St Martin's-on-the-Hill was one of many buildings in Scarborough which were damaged during the German bombardment of the town. The raid took place just as the 8.00 a.m. communion service was commencing. Despite the noise and damage, Mackarness continued with the service, before returning to the vicarage, where he found that shrapnel had entered through the window of his study and damaged the bookshelf behind his desk. Later that day, the wedding of Richard Horsley and Winnifred Duphoit continued as planned. Charles Mackarness's "sangfroid" remains a "staple" of tours of St Martin's church in the 21st century.