Not just in London, I'm in the East Midlands and the lack of indicators is a big problem here too.
If I'm a pedestrian, I need to know you're about to speed into the road I'm about to walk across.
If I'm driving, it would be good to have some warning that the car I'm following is about to turn - usually the first I know is when they brake heavily all of a sudden before they turn. Not expected, as the road is clear! Also, if you're turning left at the roundabout, then sodding well indicate that you are, I'm fed up of sitting there waiting to pull out when it turns up nobody is coming round anyway.
And another thing - it may have gotten a little bit foggy, but I am crawling along in traffic right behind you. I know you are there, so you don't need to put your rear foglights on right in my face. Similarly, if it's not foggy then you don't need your front foglights on. Those day-time running LEDs on new cars are one thing, but you're not fooling anybody in your 12 year-old Corsa.
And on the subject of lights - if it's foggy, rainy, or dark that means visibility is impaired. Put some bloody lights on so I can see you! And no, front foglights are not a substitute for headlights.
Well, that was cathartic. Can you tell I've just had the journey from hell 30-odd miles into Nottingham, then 30-odd miles back home?