[6] Lyne returned to England to attend the Staff College, Camberley, from 1935 to 1936, where his fellow students included Eric Bols,[7] Terence Airey,[8] Joseph Charles Haydon,[9] Geoffrey Bourne,[10] Walter Lentaigne,[11] Freddie de Guingand[12] and Charles Keightley,[13] along with both Henry Wells of the Australian Army and Rod Keller of the Canadian Army.

In November, he was promoted to acting lieutenant colonel (made temporary in late February) and became Assistant Military Secretary, where he was responsible for the minor details of officer appointments.

The 56th Division was then serving in East Anglia, Lyne's brigade being stationed in Nacton, Suffolk, and in June orders were received to prepare to mobilise for active service overseas.

[22] The division formed part of the Indian XXI Corps of the Tenth Army, which was given the role of preventing the Germans from reaching the Persian Gulf from the Caucasus.

In March, the division (minus the 168th Brigade) was ordered to join the British Eighth Army, then fighting in the final stages of the Tunisian Campaign.

Although the attack began well, a counterattack on the first objective sent men of the 2/5th Queen's, commanded by Lieutenant Colonel John Whitfield (who would later be GOC 56th Division), back to their own start lines.

[23] With the campaign over, the division, now commanded by Major General Douglas Graham after Miles was severely injured on 5 May, was in late May sent to Libya to rest and absorb reinforcements, as well as to train for amphibious operations in preparation for the Allied invasion of Italy.

The 169th Brigade destroyed thirty-nine aircraft on the ground but, despite support from a squadron of Sherman tanks of the Royal Scots Greys, German resistance was stubborn and they refused to move off the airfield and only fell, almost four days later, after fierce fighting, with heavy losses to all three Queen's battalions.

[23] Over the next few days Lyne's brigade, holding a large sector of the front with too few troops, was reinforced with a company of Royal Engineers acting as infantry.

[23] With the Germans, who had been concerned mainly with attacking the division's right – where there had emerged a large gap between the US and British forces – on the retreat from Salerno on 17 September, due to the situation turning in favour of the Allies, the brigade, along with the rest of the heavily battered 56th Division, spent the next few days in further fighting in an attempt to break through the mountain passes on the path to Naples.

[23] The capture of Naples followed days later, with Lieutenant General Richard McCreery's British X Corps (under which command the 56th Division was serving) advancing on the left of the US Fifth Army, reaching the defensive line on the Volturno river by 9 October.

On 15 October Major General Gerald Templer arrived to take command of the division, and Lyne returned to the 169th Brigade.

[23] Returning by early December, the division, with Lyne's brigade playing a major role, was supported by a very heavy artillery barrage and took part in the second attempt to capture Monte Camino, which was taken and the Germans finally thrown off the mountain.

The division was serving in Kent as part of XII Corps of the Second Army, commanded by Lieutenant General Miles Dempsey.

[28] At the same time, in the first week of August, the 59th Division, with the 56th Independent Brigade temporarily under command and supported by elements of the 34th Tank Brigade, launched an attack over the Orne river and after much hard fighting – with Captain David Jamieson of the 7th Battalion, Royal Norfolks securing the 59th Division's first and only Victoria Cross – secured a bridgehead at Grimbosq, before advancing to Falaise where it held the edge of the "pocket".

[30] On 22 November, Lyne was, unusually for an infantryman, selected to become GOC of the veteran 7th Armoured Division, in place of Major General Gerald Lloyd-Verney who, his superiors believed, had been over-promoted.

Lyne did not see his first action as an armoured commander until mid-January 1945 when, serving in XII Corps, it fought in Operation Blackcock, the attempt to clear the Roer triangle.

Although he remains largely unknown, Lyne was a highly competent and experienced battlefield commander, gaining respect from both his superiors, most notably Montgomery and Dempsey, and subordinates alike.