I think we are now at the nub of the question.
NATS want to reduce staff to the point where Class D access is compromised.
ICAO, SARG, DfT, Licences, Agreements, and particularly ACPs say that Class D should be accessible to VFR flights.
It is therefore a matter of policy.
That is what I am lobbying about.
(And, Eastern Guy, sorry if I have used too many double negatives, but if you read what I have written, I am completely accepting that Class D should be about IFR/IFR and IFR/VFR separation (though even that exceeds my understanding of ICAO) but the issue on the day in question was only VFR/VFR separation, and that is not required in Class D.)
TDM, no, Thames only provides ATSOCAS to its own IFR traffic and to traffic about to enter the Zone.