Well, according to a few cyclists cyclists that saw it - and I think a van driver behind - the car appeared to swerve into the rider. I didn't see the impact but rather was drawn to look over when I heard (and then saw) the crunching of the bike under the wheels of the car.
Rider down just now.
It actually looked deliberate...
The guilty party - a black Range Rover with reg T2 FLV - fled the scene.
Help is on the way.