Complex sentence: He was a member of the Guidelines Development Group for Attention Deficit Disorder (ADHD) at the UK National Institute for Health and Care Excellence (NICE) and has served as an external clinical assessor for the National Health Service Ombudsman.
Split into simpler sentences: He was a member of the Guidelines Development Group for Attention Deficit Disorder (ADHD) at the UK National Institute for Health and Care Excellence (NICE). He has served as an external clinical assessor for the National Health Service Ombudsman.