Thanks tomcs, you are perfectly correct.
We did not go to Compton Abbas today, as we went to Exeter instead. I did telephone Compton Abbas, to ask for an explanation, which was roughly as follows:-
The windsock mast, also holds the anemometer, & is technically an arial has it has a small transmiiter in the top, to relay wind speed & direction to the display in the tower.
The mast is just north of the 08 threshold, & within 50ft of the runway, so has to be mentioned under warnings in Pooleys.
"Frangible" just means that the mast is designed to collapse if hit by an aircraft. The man at Compton said no one has hit it so far, to prove if that happens!
Well ... I am still learning new things about flying
