Complex sentence: Chepstow is now part of the Arena Racing Company, also called ARC Racing and Leisure Group a private UK company, created in 2012 by the merger of Arena Leisure and Northern Racing.
Split into simpler sentences: Chepstow is now part of the Arena Racing Company, also called ARC Racing and Leisure Group. This is a private UK company, created in 2012 by the merger of Arena Leisure and Northern Racing.