r.e locking, IVA manual states: 'The fuel filler cap must either be tethered to the vehicle or be of a lockabletype where the key can only be removed when the cap is locked or anautomatically opening and closing, non-removable fuel filler cap''

Not sure if they class the actual hinged Aston top as the cap or the lockable insert. The actual Aston cap is obviously 'tethered' to the vehicle, I believe most lockable inserts 'trap' the key when unlocked?