the other fantasy is carrying a bazooka and shooting anyone speeding. optionally the weapon is futuristic and able to just vaporize the car while leaving passengers unharmed. they just suddenly find themselves sitting on the street looking dumbfounded.
Close passes are not something the police look for (excepting a couple of specific operations where they had a cycling officer) so bikecams are the only way to get the police to take any action and that is usually just to send a warning letter.
Most actual cycle deaths seem to be people crushed by lorries when turning at junctions which seems more an engineering issue - the drivers can't see etc. than bad driving.
The onus is on a driver making a manoeuvre to ensure that it is safe to do so, and turning left shouldn't just be performed blindly if the driver has restricted view around their vehicle. However, there's a lot of poorly designed junctions as well.
I believe that one way to improve the problem of left-turns is to have traffic lights that enable cyclists to go first, or allowing cyclists to treat red lights as "give way" signs or turn-left-on-red.
There's also the question of whether we should allow vehicles to use public roads if they have known "blind spots" that drivers are not able to resolve by moving their heads.
Personally, I'd like to see a far more serious attitude to road/traffic safety. When there's a fatal collision, the junction/road should be closed to motor traffic until the junction can be made safe (e.g. adding a separate cycle lane or amending the traffic lights). However, motornormativity suggests that it'll never happen.
I'm not sure the highway code rules are that appropriate for places like central London. I tend to treat the whole place like a pedestrianised area - not worrying too much about road signs but giving way to pedestrians.