Today's run was not good.
Apart from it feeling unusually difficult to run for 50 minutes my ankle began hurting about 5 - 6 minutes before the end. Now, it could be that the course was not as flat as my recent routes. Or it could be that, at the moment, 50 minutes is my limit.
Or maybe it's just a blip. After icing the area and taking some extra protein I got some advice from the physio.
The suggestion is that, for the moment, I should continue so long as it isn't debilitating. The problem is that ultra distance runners have a different perception of pain to the rest of the population ...
Will listen extra carefully to my body for the next few days.