Guthrie was commissioned into the Welsh Guards on 25 July 1959.[5] He was promoted to lieutenant on 1 June 1961[6] and captain on 25 July 1965.[7] In 1966 he became a troop commander with 22 Special Air Service Regiment serving in Aden, the Persian Gulf, Malaysia and East Africa and then in 1968 he became a squadron commander with 22 Special Air Service Regiment serving in the Persian Gulf and the United Kingdom.[8] He returned to the Welsh Guards in Münster in 1970 and, following his promotion to major on 31 December 1970,[9] he was given command of a mechanised infantry company in the 1st Battalion.[8] He became Military Assistant to the Chief of the General Staff in 1973 and, following a year as Second in Command of 1st Battalion Welsh Guards in London and Cyprus[8] and having been promoted to lieutenant colonel on 31 December 1975,[10] he became brigade major for the Household Division in 1976.[1] Guthrie was appointed a Member of the Royal Victorian Order (MVO fourth class) in the 1977 Silver Jubilee and Birthday Honours; on 31 December 1984 this rank was reclassified as Lieutenant (LVO).[11]
After retiring from the British Army,[1] he was created a life peer as Baron Guthrie of Craigiebank, of Craigiebank in the Dundee City council area, in June 2001.[35] Lord Guthrie sat as a crossbencher in the House of Lords.[36][37] He was one of several retired Chiefs of Defence Staff who spoke out in the House of Lords about the risk to servicemen facing liability for their actions before the International Criminal Court, particularly with respect to the invasion of Iraq.[38]George Monbiot criticised Guthrie for an alleged lack of understanding of international law. Monbiot based his argument on Guthrie's September 2002 statement for an invasion of Iraq and subsequent comments, in which he appeared to support launching "surprise wars", something forbidden by the United Nations Charter.[39] Guthrie disagreed publicly with Prime MinisterGordon Brown in 2008 over military funding.[40]
In 2007 Guthrie co-authored a book on ethics in modern warfare with Sir Michael Quinlan, formerly Permanent Secretary of the Ministry of Defence.[41][42]
In August 2014, Lord Guthrie was one of 200 public figures who were signatories to a letter to The Guardian opposing Scottish independence in the run-up to September's referendum on that issue.[56] He initially supported the continuance of the United Kingdom's presence in the European Union in the 2016 referendum on Britain's membership of the European Union, but suddenly switched to an advocacy of withdrawing from it less than a week before the vote was held, issuing a public warning of the ambitions inherent in the E.U. for the creation of a new "European Army", which he stated "would be a disaster".[57] He is on the advisory board of Veterans for Britain an organization with the stated aim of supporting " Her Majesty's Government in the task of restoring full sovereign control to all aspects of the defence of the Realm " following the EU referendum.[58]
Since 1 August 2017 Lord Guthrie has been the Senior Advisor to Ron Wahid, Chairman of Arcanum, a subsidiary of Magellan Investment Holdings.[59][60] Established 23 March 2015, Magellan Investment Holdings is a holding company with investments in natural resources, energy, real estate, fine arts, aerospace and defense and technology. Magellan is the parent company of two subsidiaries: Arcanum, a global intelligence firm, and RJI Capital, a merchant banking and strategic advisory company.[61][62]
On 9 June 2018 it was reported that, at the annual Trooping the Colour event, Lord Guthrie fell from his horse and had been admitted to hospital.[63] On 8 January 2019, in an extraordinary intervention in the political sphere by figures from the military and intelligence services quarter, Guthrie sent a letter, co-signed by Sir Richard Dearlove, to Conservative Party Parliamentary Constituency Association Chairs, stating that the passage through the House of Commons of Prime Minister Theresa May's Withdrawal Agreement of the United Kingdom from the European Union contained decisions which fundamentally undermined the integrity of the Defence of the Realm, and requested they take measures to discourage their parliamentary representatives from voting for it imminently in the Commons. The letter as an alternative advocated the case upon national security grounds that the United Kingdom should fully withdraw from the European Union without an Intergovernmental relationship between the two persisting after the process.[64]
On relinquishing his appointment as Colonel of The Life Guards and Gold Stick-in-Waiting, The Queen appointed Lord Guthrie a Knight Grand Cross of the Royal Victorian Order on 7 June 2019.[34] On 1 December 2020, he retired from the House of Lords.[65] His interests include tennis, opera and travel.[1]
Family
He married, on 11 September 1971, Catherine Worrall, daughter of Lieutenant Colonel Claude Worrall, Coldstream Guards. The couple have two sons.[1][36] She died from heart failure on 8 October 2022, at the age of 81.[66][67] Guthrie's younger brother is James Guthrie, KC.[68]