Fred's medial ligament cutting operation appears to be a complete success. No more sticking and she is striding out. However, she is still 1/10 lame on her off-hind in trot and worse in canter, on an anti-clockwise 20 metre circle. She is 100% sound in straight lines and clockwise.
I had the Vet out and she has had nerve blocks up to and including the stifle with no reduction in this lameness. His conclusion is that it must be muscle/ligament problem in the rump area, so, she starts a fitness programme next week, building up over 2 months with a re-assessment at the end. All work to be done in straight lines.

We will see what happens.