Found it : 1918 Straker-Squire at Brooklands
Yes! Well solved. Nearly every car maker in the UK was represented at Brooklands at some time or other - most of the races were on a handicap basis, so anything could enter, and most did. This basic form of streamlining was commonplace, so it's not always easy to recognise the marque.
This is a 15hp model, nicknamed PDQ. (Pretty Damned Quick).