Did the parkrun barefoot this morning, and fought the temptation to run most of the way. My time was roughly 47 minutes, which is actually not a lot slower than my "fast walk" of a few weeks ago.
The paving was a bit damp, so I had to ease off when I felt the feet start to feel the sand a bit much. There's a fine balance to strike here. On the one hand, you have to put some demands on your skin if you want it to toughen up, but on the other, if you just let it go all the way to bleeding point, firstly it's no longer fun, and secondly, the healing time becomes too long. It's a bit like taking up the guitar again. Keep going until you've bruised your fingertips, and you'll take longer to get back to being able to play than you do if you stop whenever it gets "too much" (which is some kind of fine balance, as stated).
I discovered (or probably rediscovered, having forgotten before) that I'm inclined to thump my heel down a bit jarringly when I walk - something one's shoes muffle away. It took a bit of time to get into a nice stride, alternating between thumping as if shod to tiptoeing forward like a brave out hunting. Seeing as it's impact that's meant to be the problem with spinal injuries, this is something to work on. Looks like the idea that walking is harmless is perhaps dependent on developing a good walking style.
I ran a bit near the end. The temptation was too great. The idea is to eventually build up (but it was meant to start later than this) to a very slow, but very low-impact run, so apart from experiments to see what makes the foot go numb, it's necessary to try running in various ways, and feeling how they impact. That's the reason for going barefoot. The ultimate aim is to go very, very, very slowly, barefoot, making use of the fact that one's bare foot is orders of magnitude more sensitive than the most responsive shoe, so that there is instant feedback to warn if the gait one's in is getting dangerous. Anyway, so far, so good.