Lamb was promoted lieutenant on 8 September 1974, captain on 8 March 1979, and in 1981 he was Mentioned in Despatches for service in Northern Ireland. In the 1988 Queen's Birthday Honours he was appointed Member of the Order of the British Empire (MBE). He was promoted lieutenant-colonel on 30 December 1990 (with seniority from 30 June 1990), and commanded 1st Battalion the Queen's Own Highlanders from 1991 to 1993. On 26 April 1994 he was appointed an Officer of the Order of the British Empire (OBE) for his service in the Gulf War in 1991, and awarded a Queen's Commendation for Valuable Service for operational service in Northern Ireland in 1993. He was promoted colonel on 30 June 1994, and brigadier on 30 June 1996, when he was appointed Commander of 5th Airborne Brigade. He then went on to join the staff of the Joint Services Command and Staff College. From 2001 to 2003 he served as Director Special Forces.