AA tower. I've been there but the fence was nigh-on unclimbable unless you have two people. Seen a report of it on 28DL, there doesn't seem to be an awful lot to it.
I'm with Oldscrote on this one - its a water tank base with the tank missing. I dont think I have ever seen an AA tower on any UK airfields. I stand to be corrected of course.
Really ? - it must be unique then as I have not seen one anywhere else on an airfield. Usually movement observation would have been from a watch office or control tower.
Moylie telling people they're wrong without referencing your "knowledge" renders anything you say meaningless. Particularly when your knowledge is ill informed.
Hydealfred there were a few Bofors AA towers similar to this in existence at one point. There was one at RAF Filton in Bristol for a long time, I'm not sure if it's still there though as I haven't been that way for a while. Concensus seems to suggest this is a bofors tower too:
I need to do a bit more investigation me thinks. The heavy conscruction seems to point more towards a water tower. Would an AA tower or observation tower require such heavy brickwork ?