I had plans for another type of post, but am completely distracted with worry over Walter. Yesterday he had a mildly upset tummy but was otherwise fine. Last night he couldn't stand up, all strength completely gone from his hind legs, although once I helped him to stand he could walk, albeit a little stiffly. The same this morning. So I rushed him off to the vet - at the moment we can't find anything obviously wrong, and he's been given anti-inflammatories. There is a possibility it might be serious, but we just have to wait and see. He's up and about quite happily now, the drugs doing their job.
So please send healing and positive thoughts to my dear sweet boy, and keep everything crossed that this is nothing more than Walter inadvertently overdoing it while playing on the beach.