totally the bikers own fault. No questions as he is the one overtaking and coming from behind. making him 100% at fault. Same would go for anyone overtaking. I am a biker and a car enthusiast, have also been a motorcycle instructor.
The biker should have been prepared for anybody he overtakes to swerve as he has no idea what they have in front of them on the road. And you can't presume that you have been seen from behind. He never gave himself enough room, never read what the car was doing as it was swerving looking to go anyway. Totally his own fault and I bet it hurt. I have been knocked of 3 times and everyone one of mine did (none where my fault and every one made me a lot of money)
