I was flying nearby and heard the radio exchange. The near-collision came as a complete surprise to both pilots. The analysis by Tom at the pilots' meeting was extremely useful and helped us all understand what happened. Kudos to the two pilots for sharing their experience and log files with the rest of us.

It looks as if the thermal had two nearby cores and the two pilots were thermaling at the same altitude but separated horizontally. The pilots were aware of others in the thermal, mostly above them, but at least one of the two in this incident didn't see the other. It may not have been careless flying but bad geometry possibly created a blind spot. Flarm would absolutely have made them aware of this potential conflict. This is why I am now a convert.

This also shows the great value of pilots sharing their mistakes with us and might help explain why those who don't (and I mention no names!) end up not being quite so well-loved by their fellow contestants.

Mike