Sims made his professional debut in June 1979, defeating Selvin Bell in a points decision (PTS).
[1] When Patrick Cowdell vacated his British featherweight title in 1982, Sims was offered a fight against Terry McKeown for the vacant belt.
McKeown unsuccessfully protested the call as Sims became the first Welshman to win the title since Howard Winstone in 1966.
However, the temporary retirement of Cowdell resulted in Sims being nominated to face undefeated Italian Loris Stecca for the vacant European featherweight title.
[5] Part of Sims' training regime for the fight involved running the 290 steps of the Newport Transporter Bridge, both up and down, ten times a day.