By 1878, Casson had become a ‘master coachbuilder’ and in consequence entered into a partnership with Cook and Co., the Malvern Link, Carriage Works in Malvern, Worcestershire. He also became one of seven representatives chosen by the Carriage Builders Institute and the Royal Society of Arts to attend and report on the carriages exhibited at the 1878 Paris Exhibition. Later that year he exhibited a series of eighteen engravings depicting facets of carriage design at an exhibition held in the Mansion House, London. In 1880, Casson took the first prize for a two-wheeled brake in an open competition at Newcastle upon Tyne. In 1990, the Worshipful Company of Coach and Harness Makers of London awarded him, not only the freedom of their company but also the freedom of the City of London, a joint honour only bestowed by that company on three previous occasions. He later became a member of the Royal Society of the Arts. In 1891, Casson took over the business, Starkey and Co, of Ross on Wye and continued to run a successful business until his death in 1909.