Young was promoted to Inspector (equivalent to Lieutenant in US police forces) in June 1937 and appointed to Portsmouth's Southern Division. In Eastney and Southsea, he first had to deal with the problems created by traffic, including ways for its efficient control and of the need to promote road safety. Young was a keen motorist, who moved from a motorcycle to a series of fast cars.
Young was qualifiedor promotion, but for someone who did not graduate the Hendon Police College and did not go to a public school, his promotion over the next dozen years was meteoric for the 1930s and 1940s.
Young wanted to head his own force and tried to become chief constable of the Isle of Wight Constabulary, before he became Acting Chief Constable of Leamington Spa Borough Police in September 1938, aged 31, at a salary of £500 per annum. One year later, he was appointed to the permanent post of Chief Constable. He was one of the youngest men ever to become a Chief Constable. In his first nine months in Leamington he persuaded the council to hire an extra twelve officers, the first increase since 1915. This meant he had 57 police officers to cover all of Leamington Spa.
He also reorganised the borough's fire brigade, and, among other police innovations, set up twelve of "police pillars", a network of two-way microphone handsets across the borough so that the public could contact police stations and civil defence posts directly. The base of the pillar contained first aid equipment while, a Leamington innovation, a flashing red light on the top called up policemen on patrol.
From November 1940 he was seconded by the Home Office for six months to Coventry after its blitz. He ran the city's police because the Chief Constable was fully occupied as Civil Defence Controller Young started the "good neighbour scheme" for bombed out civilians that he had trialled in Leamington and which was later adopted nationally by the Home Office.
Leamington's was a very small force and for a year his command was only "acting" so, from the start, Young was looking for a permanent as well as a larger command. After several unsuccessful applications (the East Riding of Yorkshire Constabulary in 1939, Portsmouth City Police in 1940, Oxford City Police in 1940), in September 1941 he was selected from a short-list of six as Senior Assistant Chief Constable of Birmingham City Police, then the second-largest police force in the UK; the salary was £1,000 p.a. He was to be responsible for training and communications - both things he was good at.
In Birmingham he started to experiment with police training. Learning by example and by demonstration is common now, but in 1941 it was a new idea and it caught the approving eye of the Home Office. He also made Birmingham the foremost British force in the use of police wireless by establishing in 1942 a "duplex" ultra high-frequency two-way radio telephone system linking every police station and every police car.
In February 1943 Young was one of the chief constables sent to the War Office Civil Affairs Training Centre for the first course for senior officers. Before the course was finished, he was transferred to the instructing staff and in June 1943 he was appointed the first commandant of the new Police Civil Affairs Training Centre at Peel House in London (with a rank as if he was a Lieutenant-Colonel in the army). He had to set up the training school for policemen and provost officers (military police) who would keep law and order in Axis territory as it was liberated by advancing Allied forces. Just after the centre was opened and its first students through their course, Young was made a Colonel and moved from the classroom in July 1943 to be Senior British Police Officer in the Mediterranean Theatre, stationed in North Africa awaiting the invasion of Sicily.
Young went ashore on day two of the invasion, and became Director of Public Safety in the first functioning Allied military government - the Allied Control Commission for Italy; in December 1943 he was given the additional role of Director of Security, responsible directly to the Commander-in-Chief for hunting saboteurs and enemy agents as well as the removal of fascist officials from public offices. In Italy, Young commanded not just British officers but the 120,000 men of the entire Italian police and had responsibility for all Italian prisons, fire brigades and civil defence. The models Young developed in Italy were later applied across Allied occupied Europe in 1944–1945, but his proudest achievement was the restoration and reorganisation of the Carabinieri, with whom he maintained an association for the rest of his life. He also fell in love with Italy, returning regularly and frequently holidaying in Positano and visiting his wartime friend Colonel Alfredo "Freddy" Zanchino of the Carabinieri.
Young became Chief Constable of Hertfordshire Constabulary in 1944 (but released from the army only in April 1945). He was in charge of 515 officers at a salary of £1,290. Still aged only 38, he had twenty-one years of experience of small, medium and large city and borough forces. From Hertfordshire, he set the pace in revitalising county police forces, pushing his police authority to spend a lot of money to improve officers' pay and conditions.
Police housing was one of the outstanding issues of the time. Young persuaded his police authority to fund a building programme so that in six years every married man in the county force would have a police house; the design and equipping of these houses was agreed between the county architects and a "housing committee", recruited through the county Police Federation, not only of men of all ranks but, at Young's insistence, of officers' wives. In 1946, he wrote:
He also persuaded his authority to buy new equipment because he wanted a modern, efficient police force. The Home Office allowed Hertfordshire to be the first force after the war to introduce a wireless system - Young adapted from his Birmingham model for rural use. To make it as effective as possible, the Home Office accepted his idea that the wireless network cover more than one county so the neighbouring county force of Bedfordshire was added.
Almost at the same time, Young was appointed by the Home Office to a committee chaired by Sir Percy Sillitoe, Chief Constable of Kent, to see if all forces needed wireless networks.
His time at Hertfordshire also saw the start of a professional relationship with James Callaghan. They already knew each other from Portsmouth, where their mothers had both worked at Agnes Weston's Sailors Rest; Callaghan had tried unsuccessfully to court Young's sister, Eileen. Callaghan was now a junior minister at the Ministry of Transport. They met up with each other again on a road safety committee and became working allies to extend speed restrictions and improve road markings; cat's eyes were perhaps the most significant fruit of their labours. They worked together again when Callaghan was Home Secretary and it was Callaghan who selected Young to go to Ulster in 1969 to implement the Hunt Report.