Mr Beck was Ravenscaur School's P.E. teacher. When he took his class running across the beaches of Ravenscaur Island he fell into a Sea Devil hatchery. He and his class were transformed into Sea Devils. (COMIC: Clara Oswald and the School of Death)
Take Mr Beck, who joined us not long before you. He possessed a certain arrogance, but has since learned his lesson. Now, he's well and truly one of us.