Brian Mackenzie was a chief superintendent in the Durham Constabulary and is a former president of the Police Superintendents' Association of England and Wales, which post he held for three years. He was vice president for the previous two years. A police officer for 35 years, he has served as an urban, rural beat, CID, and training officer. Whilst serving as a detective sergeant, Brian graduated in law with honours from London University and as a detective superintendent graduated with five straight ‘A’s from the FBI National Academy in Quantico, Virginia in the United States.

He served as head of his force drug squad and also as head of the crime computer project team, spending two years in an advisory capacity seconded to the Home Office. He is a former governor of the Police Staff College, Bramshill and was a member of the Police Training Council for five years.
Lord Mackenzie has held sub-divisional and divisional command in the rank of superintendent and chief superintendent respectively. He has been commended for outstanding police work on seven occasions, by the courts and by his chief constable.
Having travelled extensively, Lord Mackenzie has studied and lectured on police methods in Italy, Denmark, Germany, Switzerland, Norway, Belgium, Ireland, Iceland and Austria, in addition to North America and India. In May 2000, he travelled to the Russian Federation, visiting Moscow and Siberia for talks with ministers, police chiefs and business leaders on crime and security matters.