Why you should always assume the driver has not seen you

I have to agree with this. There are laws, and there is common sense.

I used to row on the Thames, with big boats coming past. As a non-motor boat I had certain rights of way, but I always remember what my coach said to me "Being right doesn't help if you are dead, stay the fuck away from other boats".

And that's the same principle I apply to cycling.

+1. I generally cycle assuming I have the same rights as any road user, BUT always try to have a plan B to account for idiot drivers - I'm not happy to put my general health in the hands of fools. I get the impression that a lot of drivers a) assume cyclists don't go very fast b) are just a pain in the arse that get in the way of real road users. If I don't think I can get out of a situation I try not to get into it. By approaching the roundabout at that speed, that cyclist wasn't giving himself enough options.