He was one of the first to join the newly formed Parachute Regiment and served with distinction in many wartime airborne operations, such as in North Africa and Sicily and Italy, until his injury and subsequent capture at Arnhem.

He was educated, initially, at Wellington College, Berkshire, but was transferred to Monkton Combe School, Somerset in 1929 due to lack of progress.

At this time Frost, who was now an acting lieutenant-colonel and in command of his battalion, was tasked to attack enemy airfields near Depienne 30 miles south of Tunis.

The airfields were found to be abandoned and the armour column they were supposed to meet up with at Oudna never arrived, leaving Frost's battalion 50 miles behind enemy lines.

[6][better source needed] In 1943, Frost's battalion, with the rest of the 1st Parachute Brigade, now under Brigadier Gerald Lathbury, was landed in Sicily during Operation Husky with orders to capture a road bridge called Ponte di Primosole.

If all had gone to plan there would have been almost 9,000 men[10] holding Arnhem bridge for the two days it was supposed to take Lieutenant-General Brian Horrocks's XXX Corps to reach them.

[6][better source needed] On 17 September 1944, as commander of the 2nd Parachute Battalion, Frost led a mixed group of about 745 lightly armed men who landed near Oosterbeek and marched into Arnhem.

[11] The battalion reached the bridge capturing the northern end, but Frost then found that his force was surrounded by the II.SS-Panzerkorps and cut off from the rest of 1st Airborne.

Frost was in command during the fierce four-day battle that followed, in which the Germans rained artillery fire onto the paratroopers' positions, and sent tanks and infantry into some of the most intense fighting seen by either side, with very little mercy shown.

While in Palestine he met his future wife, Jean McGregor Lyle, who was there as a welfare worker; they married on 31 December 1947 and had two children, a son and a daughter.

He then commanded the 44th Parachute Brigade, another TA formation, composed of part-time soldiers, before receiving promotion to temporary major-general on 11 October 1961,[13] and returning to the 52nd Division, this time as its GOC, a post he would hold for nearly three years.

[6] By the time of his retirement from the army in 1968, Frost had attained the permanent rank of major-general and in addition to his wartime decorations, had been appointed a Companion of the Order of the Bath in the 1964 New Year Honours.