Although he had a long and varied career in British films, Ashton is chiefly remembered for his work on the Hammer's horror films. After assisting Leakey on "The Curse of Frankenstein" (1957), Ashton found himself in charge of make-up for "The Hound of the Baskervilles" (1959) when Leakey, having had his retainer cut by the company's associate producer, Anthony Nelson Keys, left the company in disgust. Ashton's main effort on that film, to transform a Great Dane into the title character, was barely a success, the result only appearing briefly in the final cut. His next film, "The Man Who Could Cheat Death" (1959), involved transforming Anton Diffring into "a living corpse": "To produce all the ravages of time and debauchery, I felt that the final effect should be a cocktail of fatal diseases spreading rapidly across his body. Glandular fever, smallpox, cholera, typhus and typhoid, represented some of the ailments that Bonner had come into contact with (through his unseen travels) as a crusading physician." The result was widely admired: over a decade later the American make-up artist, Dick Smith, consulted Ashton about the effect to create make-up to age Dustin Hoffman as a 103-year-old man in "Little Big Man", and was to repeat the effect in several subsequent films.