Perhaps a totally irrelevant question. But having gone through and indeed commented several times. I don't see the following question asked. By all accounts the heli did not declare an emergency, so considering he heliport is perhaps a 1/4 mile away? The controller would have seen both visually and by looking at the metar that the weather was not suitable. Do they bear any 'responsibility' for accepting the inbound as opposed to advising heathrow there were perhaps better alternatives due to deteriorating weather?
By responsibility I am not portioning blame at all. I mean are they obliged to relay weather info with a known inbound and bad weather? Again I understand that it is down to the pilot to choose (a divert won't be 'given' to him) but surely battersea heliport would have known or at least seen the weather.
Strikes me as odd that heathrow passed him to battersea but he never made contact. No reports of battersea trying to make that contact either. If you know of a heli diverting to your field because of conditions not suitable for flight along his current route, And you can also see your weather is not great in the atz you control. Would you not make the effort to establish the contact? And make sure all is ok?
Again not putting the onus on anyone. Just an observation