Driver error. Something was wobbling around on the car in front and I let it distract me.
I was 100% 'on it', well up the top of 4th. Missed my braking point had to do the split second decision of what escape plan? Decided it was safer to lob it in straight rather than attempt the bend, then understeer/oversteer into the litter sideways and roll.
Felt pretty stupid, but lesson learnt and got away with it