Courtesy of the discussion in the Ask a question
thread... I have extracted the key aspects from that discussion
Lets look at the signals...
In Britain, trains pass on the left, so the Golden Arrow is at least on the correct track. All else being equal, semaphore signals are usually placed to give the driver the best possible view, which is on the left as the driver views it – however, although unusual, it is possible for the signal relevant to the oncoming Golden Arrow to be on the right as the driver sees it.
The arm pointing upwards at 45 degrees is seen from the rear; the driver would see a red arm with a white vertical stripe whereas we see a white arm with a black stripe.
The other (horizontal) arm presumably applies to trains travelling in the opposite direction. The colour is correct, but for the train on the left track going into the background the signal arm should have been pointing left in the direction of that track.
Additionally, this signal appears to be a lower quadrant two-position semaphore, manually controlled from a signal box. Therefore the left arm ought to be facing left, not right, and the right arm ought to be down at 45 degrees, not up.
This would indicate "stop" for the left track and "proceed" for the right track. It was not until automatic electric signalling was introduced that you had upper quadrant three-position signals.