He served as an officer of the Territorial Army from 1980 to 2013 and became the most senior reservist of the British Armed Forces.

[3] He was a Partner of Knighton White, a philanthropic and social responsibility advisory and management service.

[5] Smith was commissioned into the Territorial unit of The Light Infantry, the 5th Battalion, on 31 July 1983 as a second lieutenant (on probation).

[10] He transferred from the Light Infantry to the Royal Green Jackets as a captain on 15 April 1989 with seniority in that rank from 1 May 1987.

In 2014, he became Honorary Colonel of Northumbrian Universities Officer Training Corps and Chairman of East Anglia Reserve Forces' and Cadets' Association (until 2018).

[5] He was made a Doctor of Civil Law honoris causa by the University of East Anglia in October 2019.

Smith was awarded the Efficiency Decoration (TD) on 22 November 1994 in recognition of twelve years service as a Territorial Army officer.

[18] He was awarded a clasp to his Efficiency Decoration on 4 December 2001 in recognition of a further six years service.

[24] He was appointed Aide de Camp (Territorial Army) to The Queen on 22 February 2002.