Kim, you are very bad!
Are these in any way similar to the 'Pollution Control Valves' which are signposted along bits of the M25 ?
Inkberrow – there's a vaguely spooky looking probably military communications type building there. I rode past it once by accident. There were no black helicopters but it was before 5G. Assuming it's the same Inkberrow. Anyway, that's nothing to do with these vacuum powered valve chambers (unless it really is a pneumatic tube system for delivering top secret messages!)
Paging matthew. matthew to the sewage sludge coloured coutesy telephone please.