Are you sure that you have a genuine war time picture John? Back then the brake rod didn't fit the long forks.
Some years ago when I was curious about when the forks changed, I got this from Henk:-
The short fork is typical for the DeLuxe M20 with brake rod. The brake rod doesn't fit the long fork, it's just a little to short to fit properly.
The last photo of a deluxe M20 with brake rod is a BSA with tank number C4300302 and frame number WM20.24790. The short forks could have been used a little longer but not by much. The first photo that clearly doesn't have a brake rod and is a BSA with frame number WM20.25307, this BSA seems to have the front mudguard spacer fitted. (contract C7287 194o/41 at frame number WM20 28803… C4345395)
Half way down this document for contract C7287 is the date where the order was given to modify the forks (12/4/1941) Ron
Sorry John, I just re read your post and your picture has a brake cable not a brake rod. But I'm curious about the steering damper as that was deleted much later (1943 I think?) Ron
Here is the picture that John's enquiry is about. I'm pretty sure the steering damper knob is hidden behind the handlebar as it looks connected to the front down tube? Ron
Actually John, now I read through that document again. Item 6 is modification to fuel tank on 26/4/1941. There were lots of changes mid contract to that contract. I've emailed it to you. Ron