He worked as a dentist from 1965 to 2005, and was Chair of the Dental Protection Ltd (a professional support organisation) from 1995 to 2001.

In 1998 and 1999, Lord Colwyn was chair of the radiostation Raw FM, and of Banbury Local Radio from 2003 to 2005.

Due to commitments at the House of Lords, he stepped down as chairman of Campbell Montague International in 2008.

He was also a Fellow of the Industry and Parliament Trust and a Member of the Royal Society of Medicine.

He was president of the Arterial Health Foundation from 1993 to 2004, of the Metropolitan Branch of the British Dental Association (BDA) in 1994 and 1995, and a council member of the Medical Protection Society from 1994 to 2001.