Anyone know anything about old cars?

[eleanorjane]

I'm trying to help my father identify an old car. You can see it in this picture; it's a lovely old car my grandfather had. This photo was taken in England in the late 1930s or possibly the very early 1940s. (That's my grandfather in the super-dashing Biggles-esque motoring helmet. :))

My father thought the car was a Jaguar SS100, but has spotted some significant differences. If anyone can help with identifying the make/model I'd be forever grateful. Thanks!