Cullis managed Swansea City for just one-and-a-half games: a 1–0 home defeat to Swindon Town and 45 minutes of an eventual 4–0 defeat at Blackpool. In the second match, which took place at Bloomfield Road on 13 February 1996, Cullis' planned half-time team talk was ignored as the players took control. Christian Edwards gave the team talk and game plan instead, and Cullis resigned shortly afterwards.
In April 2003, Cullis was jailed for nine months for fraud and deception at Wolverhampton Crown Court after falsely claiming to be a highly paid marketing consultant. He was jailed again, for a further nine months, at the same court in September 2004 for handling a stolen insurance certificate and using it with intent to deceive.