Rear light removal

[yelnats69]

Can any member tell me the size of the two nuts that hold the rear lamps in position.

I need to remove mine to try and fix the parking aid, but have a real limited tool kit in the UK and nothing to fit these, they look typically like off mark size left over from the Lucas days. 

[KEN33Y]

I cannot imagine the nuts being any different to 10, 11. 12 or 13 mm well gone are the old AF sizes