The Air Ministry purchased a farm (Penyberth: Nprn, 16699), of about 250 acres for Penrhos, three miles west of Pwllheli, in 1936. The construction of the airfields was marred by an arson attack on the construction company's huts and stores by Welsh nationalists on 8 September 1936. The station opened on 1 February 1937 with 5 Armament Training camp equipped with Westland Walruses and five target towing/air-sea rescue boats working from Pwllheli harbour. Penrhos became the home of 9 Air Observers School (later 9 Bombing and Gunnery School) in September 1939. The unit were equipped with Handley-Page Harrow bombers and Fairey Battle light bombers. Early in 1940, 12 Fighter Training Squadron used the airfield for training with Avro Tutor, Airspeed Oxford and Fairey Battle planes. Bombs dropped by a German aircraft destroyed three blocks of officer's quarters, damaging a hangar and killing two men on 9 July 1940. The station was camouflaged with painted hedges and lanes and attacks were further deterred by Supermarine Spitfires from 611 Squadron and later Hawker Hurricanes from 312 Squadron. 9 Gunnery School moved to RAF Llandwrog in January 1942 and 9 Observers Advanced Flying Unit (O AFU) were formed at Penrhos in February and equipped De Havilland Dominies and Avro Ansons. Penrhos continued with a training role concentrating on air gunnery. An AML Bombing Teacher and Turret Training system was installed inside a Blister hangar utilising a screen to project footage of moving aircraft . Penrhos became a satellite airfield to Llandwrog towards the end of the war. 9 (O) AFU ceased to exist on 16 June 1945. 21 Aircraft Holding Unit (ACHU) used the accommodation until 31 March 1946. The site became a demobilisation camp for Polish soldiers and airmen, with up to 100,000 awaiting repatriation. However, when it became clear that many Poles could not return to their homeland, a permanent camp was established in 1949; it is still in use and known as the Polish Home.

Facilities for the early grass strip airfield consisted of wooden huts to which concrete buildings were later added. A Bessonau hangar was replaced by two Bellman hangars in 1939. Ten Blister hangars were also constructed. A caravan site now covers the majority of the airfield, including the bases of the dismantled Bellman hangars and the engineering section. There are wartime concrete buildings around the perimeter track, which is also extant. There is a recently constructed 400m tarmac runway which is still is use for private aircraft.

Sources include:
Defence of Britain Project
Jones, I, 2008, Airfields and Landing Grounds of Wales: North, p42-53
Sloan, Roy, 1991, Wings of War over Gwynedd, pp 106-124
Phillips, Alan, 2006, Military Airfields Wales, pp 182-8
Smith, David J, 1982 Action Stations 3: Military Airfields of Wales and the North West, pp 134-6

RCAHMW, July 2008.