OK, so I have just listened to the latest Sonia Poulson podcast with Philip Walker and it answers some of our questions about the Milbank call!
In fact it is us who forgot about one very important point, or at least I did anyway.
That is, the fact that when you dial 999 the operator asks you what service you require, ie., police, fire or ambulance! At least thats what it was in those days, remember?
So Sheila must have phoned the operator who then put the 999 call through to Milbank, which makes sense!
In fact I think thats what Bill was suggesting earlier on.
Anyway, that answers why Milbank knew where the call came from!