The letter I sent to Hans Hoogervorst in October last year remains unanswered, but it turns out it was never received, or lost.
I re-sent, but still resounding silence, so far.
Bureaucracies have three basic modes of response. (1) If the query is easily dealt with, then reply with the easy solution. (2) If the query, whether hard or easy, is out of scope, then reply politely ‘nothing to do with us’. Probably 85% of queries are dealt with this way. (3) If the query is clearly within scope, and also very difficult, then do not reply. To confirm that the bureaucracy is powerless to solve the problem would be an acknowledgement of failure, or dereliction of duty. To actually do anything about it would be equally fatal.
This explains all forms of radio silence.