I see DVLA have it as a 1958 Bristol 405, not a 403 which wouldn't be as late as 1958 anyway.
Thanks; that's more likely to be accurate than the website, although the car is pictured at a Bristol Owners Club meeting at Woburn Abbey in 2004 and I believe was described as a 403 there by its owner. I think it's far more likely anyone would turn a 405 into this than a 403...
Below is a rear view of the car; incidentally nicanary I note the registration number is different from that in the picture posted by dzima, which I think is a much later picture, so the wheels have been changed from the wires to the pierced knock-offs, rather than the other way around!