I saw that photo come up on eBay. The Sunbeam has WD16H forks (with check springs and buffer rubbers). The 'WH' numberplate is presumably the Bolton series that ran from the 1920s through to 1938 rather than a 'beute' Wehrmacht Heer machine !

The far G3L is certainly a dark colour but I wonder if it is olive drab next to SCC Brown ?

It occurred to me that the older chap in the background looked very much like Joe Craig.