This is interesting. It IS a GN, contrary to your post #6, and is owned by Ben Enticknap. I can find the car on various sites, including Facebook, Flickr and old Chateau Impney events. They all mention 1922.. However, the GN was manufactured from 1913 to 1922 almost without any major change, and it could date from any of those years. It is clearly fitted with a V-twin JAP 998cc.