Prior to becoming an actor, Sebastian found employment in the following professions:
He spent three years as a professional wrestler in London before the Second World War. He ended up quiting the profession after receiving an injury. He worked as a chef and it was during this period of time in which he gained weight and ended up weighing around 260 pounds. He also worked as a chauffeur for, British actor, Frank Pettingell. It is this job that actually got him interested in acting.