I presume that the Airport perimeter road at Bristol Airport is owned and controlled by the Airport despite being open to the public.
Bristol Airport
If you extend the RW 27 centreline from the eastern end of the runway by 1000 metres which is near enough the amount of clearway the clearway extends well outside the airport boundary. Other than the minor road just off the western end (which would I'm sure be under control of the airport authority) the only other public road is just east of the RW 27 threshold. For this reason RW 09 only has about 60 metres of clearway.