Rode Gamble and cantered for 10 minutes. No probs -- other than a stumble by Gamble which caused a temporary minor injury to me -- not in my legs, though. I was able to talk normally in 2 minutes or so after the stumble.
Physiotherapist Craig came over and gave me a printout of the exercise I should be doing. He did more ultrasound plus lots of intense massage of the leg.
I'm starting to think that the riding could actually be helping me. Its not generally weight bearing, but it does get me using quite a range of motion and different muscles -- particularly when doing a posting trot.
2 weeks after the injury and I'm feeling quite good. Still tight in my hamstring, but I'm now walking without a limp.