Cleaned, polished and treated to some new rear tailgate gas struts!
Blimey, you've got the lesser spotted battery cover (and a bolt missing from the RH bonnet latch.....).
That bolt has been absent without leave since before I got the car. I guess I'll put one in at some point but I think there's a load of stuff to move out of the way - don't think it is a captive nut?
Weirdly, that top panel is the only place on the car with any signs rust - I wonder if a previous owner had a battery acid spillage as I've not seen another similarly affected. I keep it clean (ish) so hopefully that should stop it getting any worse.