I’m worried about my dog. Dyson is now 12 – nearly 13 - which isn’t a bad age for a Labrador. If you aren’t a dog person, bear with me. I will get to the point.

Why is he called Dyson? It’s really pretty straightforward. When we first had him, we noticed two things right away. First, he was yellow. Second, he scuttled around the kitchen floor hoovering up crumbs. Dyson fitted the bill perfectly.

He has been a simply wonderful dog. Back when he was fit, he and I trained together for the London Marathon. Well, to be honest, he was more intelligent than that.

He noticed that most of our runs involved going somewhere and then turning round and coming back again, so after a while he realised that the sensible thing to do was sit near the start and wait for me to come back. The effort and energy it saved him must have been extraordinary.

But it didn’t save his knees. His knees should have been recalled to the manufacturer long ago. Instead they kept giving way and he ended up with bilateral tibial osteotomies with titanium arthrodeses. I keep joking that he’s worth a fortune in scrap. But it’s no joke.

Over the past few months he has started to struggle. He still absolutely loves being with children, and tolerates their teasing and whisker pulling with the most remarkable placidity, even when a toddler accidently kicked his testicles. He loves his food, and he loves the idea of chasing a tennis ball and going for a walk. However, all too often he will come back from a walk struggling with a limp. And he does seem to get exhausted much quicker than he used to.

Are we being cruel and selfish in keeping him going? Is it time for him to be put to sleep?

Isn’t it fascinating how a question like that has become the norm? Many dog owners talk about the difficulty of knowing when it is the right time for a dog to be put to sleep. When talking of humans who are suffering we often say ‘you wouldn’t let a dog suffer like that’.

We have absolutely accepted that having a dog killed is perfectly acceptable. But doesn’t that language jar? Rather than saying ‘killed’ what I should have said was ‘put to sleep’ – an absolute euphemism, as softening as saying someone who has died has passed away.

Thankfully, he’s always been insured, or the rising cost of care might have become an issue too.

Without getting into the incredibly complex topics of euthanasia or assisted suicide, it is worth noting just how easily such a concept can move from being an exception to the norm.

Many people would think that it would simply be cruel to wait for Dyson to die naturally. They would probably say that he will have suffered too much by then, and we have been uncaring and selfish to preserve his much loved life with us.

So what is the risk that this could become the norm for humans too? One day might my children and grandchildren have a discussion about whether it is cruel to keep me going, or if it is now time to have me ‘put to sleep’?

I’m not being facetious. I’m not equating a human life with a dog’s life. What I am doing is noticing just how easily a concept like being ‘put to sleep’ can become the unremarked norm. Is that what we really want?

But my worries about Dyson can wait for a while. He’s just nudged my leg in the way he asks for a walk. It may be a short one, but we’ll both enjoy it. Even if he limps on the way home . . .