This week I'm starting to increase the distance a little after a step back last week. The basic half marathon distance felt to be the right point so long as it was done gently. I made a great effort to start very gently (not all that difficult as all my joints were stiff) and to aim for an even pace. I did very well on the effort aspect as illustrated by my heart rate.
Pacing was fairly consistent but I should have been a bit faster in the second half to match the downhill gradient and give an even GAP. I was held back a bit by discomfort related to my right ankle, I feel it was tightness, or even mild cramping, of the peroneus muscles as it was a few inches above the level of my shoes. I'm going to the physic on Monday so I can hear her opinion.
I'm gradually coming to the decision my right ankle is irritated by lengthening of the muscles as much as the edge of the shoe. That is a low heel drop shoe is part of the problem.