Hello Gordon !
First off I must say that the pics are quite mouth-watering ; an excellent example of an AA battery.....
I'm getting into the realms of guesswork here, but my thinking ( aided by pics in my trusty copy of Hogg's
'British And American Artillery Of WW2' ) is that there would have originally been one gun with an 'emplacement'-type fixing ( possibly mounted on the pipe-like object in the pictures ). The ( fascinating ) object in the last two pics
looks like part of the 3.7 Mk 6 field/AA mobile mounting ( rather similar to an 88...).
Could a mobile gun or guns have been moved up there at some time to bolster the defences ?
As I said, strictly musing out loud here.....