Having quietened my concern yesterday George fell on the steps today and couldn't get up so we've had a trip to the vet.
Basically he's getting old. Dodgy joints, thick knees, probable osteo-arthritis. We're trying him on pain-killers to begin. See if they ease the pain and help him move more easily. The vet also suggested massaging his legs for him.
George will think he's in seventh heaven.
If these don't work ... well, they'll try something else.
Relieved it's not his heart but sad to think he's been in pain, even it is just a nagging ache rather than acute. We were lucky with Harvey: he made it to the end with just cod liver oil and glucosamine supplements. Could get expensive. Thank goodness we have the NHS supplying our medicines.