 In 1905, Ayrton joined John William Simpson's practice, and from then on he carried out most of the firm's design work.He became a partner in the firm in 1910 and was elected a Fellow of the Royal Institute of British Architects in 1920, having been proposed by his old master Lutyens and by Sir Aston Webb, who at the time was President of the Royal Academy.Simpson's practice included much work for schools, and Ayrton was the architect of a new chapel for Gresham's School, Holt, constructed in knapped flint and limestone (flushwork), with two angle turrets and an embattled parapet, between 1912 and 1916, which is now a listed building.