Popham panels were first mentioned in a post for 5 April 1918. They were the possible subject of a hard-to-read log book entry while Greg was at Yatesbury:
To recap, Popham panels, or T-signalling panels, were a means of ground-to-air communication. They were introduced towards the end of the war. Their use was principally by the infantry, as an alternative to the 12′ x 1′ “ground strips” used by the artillery to make up letters and symbols. I would guess that the ground strips were more favoured by airmen as they were larger and easier to see. But the smaller size of Popham panels would have made them much more practical for infantry use.
Instruction in Popham panel reading was certainly undertaken at Hursley Park. Dave Key’s post for 11 May 2018 on The History of Hursley Park website shows a course paper (the third image of the post) that refers to the following.
2. Lecture Popham panel & its use. Procedure of mess-
ages Battn. & Bde. H.Q. & message dropping.
Message pads & tracings-Flares - Final
Report & Interview
Greg may have attended a lecture like this, perhaps on a non-flying day like today.
And when it came to the…
6. Practical. Popham Panel Reading
…then this is how it would have looked from the ground:
Greg’s pilot’s log book doesn’t contain any indication of Popham panel practical work at Hursley Park/Worthy Down. Maybe he just didn’t record it, or perhaps he was already specialised in the ‘ground-strips-and-artillery’ stream.