"The Polish Air Force in Britain, 1940-1947" Fairey Battle, L5271 'U', of No. 18 Operational Training Unit, circles the airfield at Penrhos, Caernarvonshire, prior to landing. Polish personnel and aircraft of 18 OTU were detached to No. 9 Bombing and Gunnery School at Penrhos for armament and firing practice in the summer of 1940.