It was obviously the battery and there was me thinking I'd been clever in driving around the bypass to keep it charged up, rather than just going the shortest way to the Co-op. G of course started to catastrophise, as he always does if something goes wrong, which makes any problem much worse than it need be.
Anyway, the first problem was the food shop, so I trundled into town with the shopping trolley and popped into the garage (which is all of 5 minutes walk away) en route. They said if I gave them the key on my way home, they would collect the car and have a look at it.
Obviously I couldn't get everything on the shopping list without the car, but I got the essentials and trundled the (much heavier) trolley home again, dropping the key into the garage as I went past. Shortly afterwards the car disappeared and I had a twitchy day, unsure if it was just a flat battery or something more serious.
At around 3.45 p.m. I phoned to see how the car was and they said they'd fitted a new battery and it was ready to collect. Although the car is still quite new to us, it's around 6 years old and batteries don't last forever. The very cold weather overnight must have been the last straw for it. With hindsight, it had been losing power over the last few weeks because it sprang eagerly into life when I started it to drive it home. For the past few weeks, there has been a moment of hesitation before the engine fired.
So all is well (I hope) and we've decided that now we're not in lockdown, we ought to make a point of driving to different places to go for walks. We've both just been starting our walks from home, which was what you were supposed to do during the tightest restrictions, but we can venture further afield now whilst still avoiding people.