strong wind?
 

have a look at this

BBC NEWS | World | Wind flips plane over on runway

I reckon it has nothing to do with wind.
He is too fast...is missing his turn off from the runway, hits the brakes hard (left side more than right) trying to make the turn, realises he wont make it, and straightens out, and now realises he is heading towards the grass, so to avoid going onto grass he jumps on both brakes hard, and upends the plane.

looks like another good bit of journalism.....

Also presumably he was landing into wind...

I may be wrong, but I couldn't see any use of the rudder or ailerons after touch down.

What a shame damaging such a splendid aeroplane; at least the driver got out of the wreckage.

I am not a tail dragger pilot but to me it looks as if he landed too fast. The tail stayed high for most of the ground roll. he then swerved towards the grass and the aircraft gently flipped over.

Pace

Downwind landing? The tail is down at times, without the aircraft ballooning up, which would happen if airspeed was too high, as opposed to ground speed.