On the climb, he kept looking down as was clearing having problems. I thought it was a back wheel puncture initially, but I think it was something to do with the gears. He loosened something off at his pedals, was possibly using track pedal, and then just got off. Bike was thrown to the right and he walked about 10 yds away to chat to someone in the crowd. The camera panned away and then a few mins later a picture of him riding again.