Complex sentence: The first darts player who was inauguarated into the Winmau BDO 9-Dart Club was John Walton in January 2013 for previously becoming the first and only player to record a nine-dart finish at the Winmau World Masters in 2007.
Split into simpler sentences: The first darts player to be inaugurated into the Winmau BDO 9-Dart Club was John Walton in January 2013. He, previously, became the first and only player to record a nine-dart finish at the Winmau World Masters in 2007.