Sirens

If the symbol of London is the red telephone box then the sound is the siren. Every time you walk along a road either an ambulance or police car will come zooming past you with sirens blaring. You never really know if they are off to an emergency or trying to get back in time for their lunch break. Either way it's pretty annoying. Especially in our area where it emerges there are 3 hospitals and a police station in a 500m radius. Great for emergencies but not so cool for late morning lie-ins.