In 1947 Walt Disney hired Watkin to adapt the stories of Herminie Templeton Kavanagh featuring Darby O'Gill. The project was finally realized in 1959 as "Darby O'Gill and the Little People". By that time, Watkin had written numerous other screenplays for Disney. The first of his Disney screenplays was "Treasure Island" (1950), adapted from the Robert Louis Stevenson novel. Three screenplays followed ("Beaver Valley", "The Story of Robin Hood and His Merrie Men", and "The Sword and the Rose"), which were produced by Disney in Great Britain. The popular Disney television serials "Spin and Marty" (1955–1957) were adapted by Jackson Gillis from Watkin's 1942 book "Marty Markham". Watkin was producer of Disney's 1956 Adventure film, "The Great Locomotive Chase".