The young fox is still limping and tonight I managed to get some more photos of the injury. 
Close up showing swelling
I received one suggestion that it could be a tick embedded in the paw (thanks Denise), but I'm not sure whether tonight's photos help confirm that or not. So far as his movement is concerned he is still carrying the foot when he moves at more than an slow stroll, as you can see here.
Carrying the injured foot
When he ambles the foot does go down, and he appeared to be putting weight on it when standing (at least some of the time).
Standing on the injured foot
At one point he heard something in the shrubs and darted off at speed, so his general ability to behave just like a fox doesn't seem unduly compromised. For the time-being then, I'm simply monitoring the situation to see whether he recovers. As long as he's fully mobile (which he is), not showing obvious distress (which he isn't), it seems better to leave him in the territory (which he likes).
Camera note: Photos taken with the Sigma 105mm F2.8 EX DG macro lens.
SittingFox
12 Oct 2007Hopefully he'll remove whatever it is himself before much longer. Or, if it is a tick, presumably it will be satiated and fall off soon.
KayFour
12 Oct 2007I hope he will be all right!
Flying Red Fox Blog
12 Oct 2007Hope he gets better:) Thats a good idea not to interfere yet because it will probably resolve itself.
Words
13 Oct 2007Just have to wait and see what happens, but he seems ok otherwise and in all other respects his behaviour is pretty normal, so I'm not going to panic (yet).