Jaggard joined the RM in 224 Squad on 8 July 1935 at Deal. His Regimental Number was: Chatham/X1211. After recruit training and gunnery courses he was drafted to HMS Resolution, a Revenge class battleship, stationed in the Mediterranean. Having received superior reports he was promoted to Corporal on 18 April 1938 and posted briefly to HMS Curlew, a light cruiser, and volunteered for flying training. On 1 May 1939 he was transferred to the RN on probation as an Acting Leading Seaman to commence pilot training on No 4 Naval Pilots Course. Other Royal Marines on his course were; Lieutenants Cheesman, Jolliffe, Marryat and Wright, Corporals Chapman, Lyall and Yarde (the latter did not qualify). His Elementary Flying Training took place at Gravesend and Rochester before graduating to No 7 FTS at Peterborough on 2 July. He completed flying training on 3 December1939 and was promoted to Acting Petty Officer Airman the next day; his FAA number was FX 82594. Immediately he commenced seaplane training at RNASs Lee-on-Solent, Donibristle and Ford.

On 2 July 1940 Jaggard was posted to 700 Squadron for HMS Manchester, a Town class light cruiser, as a Walrus pilot until 10 January 1941. He qualified for the Atlantic Star and was confirmed in the rank of PO Airman. During his period, Manchester was engaged in operations off Norway and in the Mediterranean. He then joined HMS Berwick, a County class heavy cruiser on 4 May 1941 until 1 June 1942. During that time Berwick was engaged escorting convoys to North Russia, Iceland and operating in the northern North Sea.

For the rest of the war Jaggard was employed as a Maintenance Test Pilot, firstly at HMS Fieldfare, RNAS Evanton, near Invergordon on the Moray Firth, from 1 October 1942 until 28 August 1944. During that period RNAS Evanton was engaged installing and repairing aircraft with Air-to-Surface Vessel [radar] (ASV), a radio homing equipment designed to aid aircraft make basic instrument approaches to airfields or ships. For the pilot this instrument approach technique required a high degree of skill and nerve; the equipment was rudimentary. It did not provide the pilot with any instrument which could be interpreted visually but only a sound signal which varied according to whether the aircraft was on track heading towards the transmitter or to the left or right. Whilst serving at RNAS Evanton Jaggard was promoted Chief Petty Officer Airman on 1 May 1943.

On 29 August 1944 Jaggard was posted to RNAS Condor for a year. His service record does not specify his duties or the aircraft he flew but for a short period in October 1944 he was detached to RNAS Hinstock, in Shropshire. Hinstock was the FAA's Advanced Instrument Flying School where pilots were being taught instrument approach techniques using the equipment Jaggard had been testing at Evanton. Jaggard left RNAS Condor on 17 August 1945 to attend a Flying Instructors Course at RAF Upavon. He was then posted back to RNAS, Hinstock as an instructor. During this tour he was detached for two months to RNAS Burscough in Lancashire, which at that time had Radar Training as one of its roles.

In April 1946 Jaggard returned to RNAS Lee-on-Solent for four months and on

19 August 1946 was promoted to Acting Warrant Flying Officer. His next appointment was to 799 Squadron on 18 August 1946 to 13 May 1948 during which he was commissioned as a Lieutenant on 25 December 1947. 799 Squadron's task was described as a 'Flying Check and Conversion Refresher Squadron' and its aircraft types at that time included Seafires, Sea Otters, Fireflys, Barracudas and Harvards. He was then appointed to HMS Annet as the Navigating Officer and to qualify for his watchkeeping certificate. Annet was an Isles class trawler and believed to be the last coal burning ship to fly the white ensign.

From Annet Jaggard returned to flying as a Staff Instructor at the Central Flying School. It was during this tour that in 1953 he was awarded the Air Force Cross in the Coronation Honours. Jaggard was then appointed to an exchange posting with the Royal Canadian Navy at HMCS Shearwater and served with its Fixed Wing Utility Squadron designated VU 32. It was during this period that the RCN was introducing jets into service and it is most likely that Jaggard flew T 33s and McDonnell Banshees as they arrived at the base – the Banshee was the only jet to enter operational squadron service with the RCN. It was during this tour, his last flying appointment, that Jaggard was promoted to Lieutenant Commander with a seniority of 25 December 1955. He ceased flying in 1956 after a very full and varied career having completed 4268 jet and piston hours including Walrus, Barracudas, Fireflys, Avengers, Harvards, Meteors, Vampires and others including, quite possibly, the T33 and Banshee. It is highly probable that after Major Partridge, Jaggard was only the second RM, or former RM, to fly jets and the only one as an instructor.

Jaggard's final appointment was to HMS Bulwark as the Aircraft Control Room Officer during the Suez crisis. He retired as a Lieutenant Commander on 29 July 1958 and became a schoolmaster in Chichester.