Magpies in distress

I’m in London. There are magpies and seagulls in the trees at the bottom of my garden. I’m in London so my garden backs on to neighbours gardens. 
this morning two adult magpies have become distressed. I think a nest has fallen but I can’t see over the fence. And I think I can hear little magpie bleets. 
what can I do? Is there anyone that come over with good ladders and assess the situation? The adult magpies haven’t stopped crowing for about an hour now.