Career
Articled to John Belcher, Johnston was notable for his sensitive conservation and restoration work on many churches in the south-east of England and other historic buildings. He also designed 24 World War I memorials and was appointed as Chichester Cathedral"s in-house architect. Johnston was vice-president of the Bachelor of Applied Arts and Surrey Archaeological Society, and was "a pillar of the Sussex Archaeological Society".
He wrote several historical works, although much was not published in his lifetime.
He lived at Sussex Lodge, Champion Hill, Camberwell and was buried at West Norwood Cemetery.