Well, the bloke in the car is definitely at fault. He's turned right in front of you. However, as a rider, unfortunately, we have to anticipate this sort of brain dead activity.
Personally I slow down for these in anticipation of the sort of action that Mr. Brain dead carried out.
Always ride as if every else Is a wanker and they're determined to kill you
Yeah, that^
You do have to mistrust any indication, they're almost always wrong on roundabouts.. But that doesn't mean the rider is in the wrong for not anticipating the drivers' mistake, driver muppet was in the wrong, I'd have had a word too..
Remove all indicators from vehicles, they're rarely used properly and, as a result, even a correctly used indicator has to be ignored.. They have brake lights to let you know they're slowing down, use your head.. Hazard lights don't magically make it possible to drive through your car, it's still causing an obstruction, and not having them on doesn't make a badly parked car invisible..
Remove all indicators, they're pointless..