Action at 2:20. I didn't see him, bu he had seen me before collision occured, fortunately.
Apparently there were two cores in a thermal, and we started circling in opposite directions.
I should have been on high alert as there were multiple people around at similar altitude, but my focus was on coring the thermal with a guy on red Phi glider.
Note to self: weak lift, lots of people = potential trouble, keep your head on a swivel.