Complex sentence: Centigon is today a division of the Carat Security Group but it traces its roots back to coach builders O'Gara-Hess and Eisenhardt and Sayers & Scovill.
Split into simpler sentences: Centigon is today a division of the Carat Security Group. The company traces its roots back to coach builders Hess & Eisenhardt and Sayers & Scovill.