Why you should always assume the driver has not seen you

According to the shadows the sun is behind the car?

Also...the driver has the sun in his/her eyes, coming from directly behind the cyclist, so would not have been able to see much detail from what I presume was a quick squinted glance ahead.

The rider wouldn't have been able to make eye contact with the driver because of the glare on the windscreen, so should have adjusted his positioning accordingly done a huge skid across the roundabout to alert the driver to his presence.