Although there was no flying for Greg today, it could well have been sometime around now that he got his first glimpse of an enemy aircraft, in form of a Fokker Eindecker E.III.
One of these aircraft was known to be at nearby Upavon for part of the war, and it is quite plausible that trainee pilots from Yatesbury would have been shown what a real German aircraft looked like, if only as part of their necessary instruction on enemy aircraft types.
According to Wikipedia:
Only one original Eindecker remains. On 8 April 1916, a novice German pilot took off from Valenciennes with a new E.III (IdFlieg serial number 210/16) bound for Wasquehal but became lost in haze and landed at a British aerodrome east of St. Omer. He was forced to surrender before he realised his error and could destroy the aircraft. The E.III was test-flown against the Morane-Saulnier N and other Allied types at St. Omer before going to Upavon in Wiltshire for evaluation and finally going on museum display. It now resides at the Science Museum in London. Immelmann’s original E.I, with IdFlieg-issued serial E.13/15, also survived the war and went on display in Dresden, where it was destroyed by Allied bombing during World War II.