A graduate of the Royal Military College, Sandhurst, de Guingand joined the West Yorkshire Regiment (Prince of Wales's Own) in December 1919.

He served as Military Assistant to the Secretary of State for War, Leslie Hore-Belisha, from 1939 to 1940, in which role he had exposure to the most senior officers in the army and developed skills in diplomacy.

On graduation he chose to join the West Yorkshire Regiment (Prince of Wales's Own), which had sponsored the Officers' Training Corps unit at Ampleforth.

Overseas postings to colonial units were a popular option for young subalterns at the time, as they offered higher pay, greater responsibility, and occasional excitement.

When Smith found out about it, he reported it to Wavell, who ordered de Guingand to cease forthwith, as he feared that it would affect the morale of the expeditionary force in Greece and become self-fulfilling.

[33] In February 1942, Dorman-Smith, by this time Deputy Chief of the General Staff (DCGS) at GHQ, recommended de Guingand for the vacant post of Director of Military Intelligence, Middle East, with the rank of brigadier.

[39] Ewart could speak German fluently and Williams, as a trained historian, was accustomed to drawing information from disparate sources together to produce a larger picture.

[52][53][54] Montgomery moved the Eighth Army headquarters from Ruweisat Ridge back to Borg El Arab on the Mediterranean coast, about 20 miles (32 km) south west of Alexandria, where it was collocated with that of the Desert Air Force.

[56] De Guingand and Williams concocted a ruse whereby they prepared a fake "going" map indicating that an area of soft sand near the ridge was suitable for vehicles but it is uncertain as to whether the Germans were fooled.

De Guingand urged that the Eighth Army carry out an immediate counter-attack but Montgomery did not consider that it was ready for this and passed up the opportunity in favour of a set piece battle.

[61] By 29 October, the Prime Minister, Winston Churchill had become concerned at the lack of progress and sent Alexander and the Minister-Resident for the Middle East, Richard Casey to investigate.

Montgomery convinced Alexander that matters were well in hand but de Guingand had to call on his diplomatic skills to dissuade Casey from sending a cable to London indicating that the outcome of the battle was still in doubt.

It was won on 2 November and two days later de Guingand dined with Montgomery and General der Panzertruppe Wilhelm Ritter von Thoma, the commander of the Afrika Korps, who was now a prisoner of war.

[63][64] Recurrent problems with gallstones struck de Guingand several times, often at crucial junctures and had the doctors had their way his tenure as the Eighth Army chief of staff would have been a short one.

[65] "The reaction of the bon viveur to his illnesses was unusual", Richardson later wrote, "he could not be called a hypochondriac, as there were very real, but he seemed to take an obsessive interest in their manifestations, and had an irrational faith in his many pills, and developed close friendships with his assorted medical advisors, so much so he was often in doubt whose advice to accept".

[67] While on leave in Cairo, De Guingand married Arlie Roebuck Stewart, the Australian daughter of Brisbane businessman Charles Woodhead, on 17 December 1942.

She was the widow of a fellow officer in the West Yorkshire Regiment, Major Hugh Dalzell Stewart, who had been killed in the Battle of Keren in 1941 and had been working in Cairo for an intelligence organisation.

[70] He was advanced to Commander of the Order of the British Empire on 26 February "in recognition of outstanding services during the operations resulting in the capture of Tripoli" at the conclusion of the Western Desert campaign.

[72] De Guingand and Montgomery discussed what could be done to retrieve the situation and resolved to strengthen the left hook manoeuvre being carried out by the 2nd New Zealand Division (Lieutenant-General Bernard Freyberg).

Unable to devote much time to it but concerned at how it was progressing, Montgomery decided that de Guingand would go to Cairo as his deputy, in charge of the planning group known as Force 545.

On taking over the planning for Operation Husky, he became concerned that it called for a series of dispersed landings based on the assumption that the German and Italian forces would not mount a fierce resistance.

Montgomery listened to de Guingand's appreciation on 23 April and then sent a message to the Supreme Allied Commander, General Dwight D. Eisenhower in Algiers, urging that the invasion plan be changed to concentrate the landings.

It was not the normal practice in the British Army for generals to take staff with them from one assignment to the next but Montgomery judged correctly that his fame as the victor of the Battle of El Alamein would overcome any objections.

[93] Montgomery's rejection of the Overlord plan did not sit well with the COSSAC staff, who now formed part of Eisenhower's Supreme Headquarters Allied Expeditionary Force (SHAEF).

[101][102]In the lead up to Operation Overlord, Montgomery left dealing with the details up to de Guingand and the staff, while he spent most of his time touring the country and talking to the troops.

He chaired the daily staff conferences and attended inter-staff meetings with his opposite numbers from the Royal Navy and RAF, Rear Admiral George Creasy and Air Vice Marshal Philip Wigglesworth.

Although Odgers liked him, Russell had an abrasive personality and no battlefield experience, which made it hard for him to earn the respect of the more operationally experienced officers at Tac HQ.

[116] He then arranged to meet with the war correspondents committee, which was chaired by Alan Moorehead and expressed his reservations about the news coverage of the battle and its effect on inter-Allied relations.

[137] On the occasion of his retirement on 9 December 1971, de Guingand strongly criticised apartheid and the government of South Africa, saying that it had become a pariah state with a network of despicable laws.

[129] The book became a best-seller; it was serialised in The Times and ran through seven editions and two paperback impressions, but de Guingand unwisely directed his literary agent to negotiate a lump sum from the publisher, Hodder & Stoughton, instead of the royalties provided by the default contract.