Peter, what suggests it is an F rather than a J1? I notice the wheels and tyres look different. The rear brake drum seems to be larger than standard, or is it that the rear wheel is smaller than the front?
Just sense the it is too long in the bonnet for a J, but I have to say your photo from a similar angle seems convincing. I would like to set up a photo shot with a J1 before I am finally convinced though...