There was a police helicopter, and then an air ambulance, it flew over our house several times with a siren (we assumed because they were trying to clear people on the common so they could land). I never knew air ambulances had sirens! I wondered what had happened too. 

If it’s the one that was above our house for about half an hour I don’t think it was an ambulance - it was blue - so loud - possibly police or news?

We drove past Wandsworth Common yesterday afternoon (late) and saw that an ambulance was trying to land. I think it was an air ambulance. Does anyone know what happened?