It's interesting how sitcoms evolve to reflect the times they are made. And not just because of now questionable attitudes to race and sex. If you look back at sitcom icons over the decades charcters that would have been portrayed as colourful or eccentric would probably now be described as neurodivergent. From Hancock to Fawlty to Brent they would all have some kind of condition.

And so we come to Only Child, which tackles further burning issues of today. When Richard (Greg McHugh, from Fresh Meat and Gary Tank Commander) goes to visit his widowed dad Ken (Gregor Fisher, aka Rab C Nesbitt) in a small Scottish town we initially see Ken's antics – barking like a dog, mixing up his pills – as eccentric. But gradually a bigger picture emerges. It is not spelt out at first but I'm guessing we are looking at a storyline trying to find the humour in dementia.

If I'm right – and i may not be – this is an interesting development. There have been plenty of single parent and adult child comedies over the years, from Home to Roost with Reece Dinsdale and John Thaw to this year's Daddy Issues. Only Child is pretty mild compared to Daddy Issues – Ken doesn't as Richard to send dick picks for him – but the same dynamic is still there. Friction on the surface but a lot of love underneath.

And it helps that both the writing, by Bryce Hart, and the performances are top notch. Some of the set-ups are pretty route one, from tech problems to sharing a bed that involves the obligatory fart joke, but the pace is pleasingly gentle and the timing spot on, so that even when you can see a punchline coming a mile off you still can't stop yourself from smiling. It is moving too. And will be relatable to many of a certain age.

There are nice running gags too – such as the literal running gag of a local petty villain who is aways too busy on the rob to chat to his old mate Richard, who is now a semi-famous actor in a Midsummer Murders-type series. Jennifer Saunders plays Richard's unseen agent Sally, very much channeling Jane Plough from Toast of London, breaking bad news to him about his job on the phone while ordering a large Cab Sauv in a bar.

Richard is only supposed to be visiting for a few days, but when his TV series is abruptly cancelled we know it means he is going to be around a lot longer than planned. Even when he is sitting on the station platform bench waiting for the southbound train. Ony Child might not sound up your street but you would do well to stick around longer than you plan too. 

BBC One, Fridays at 9.30pm, wtahc the whole series on iPlayer

picture: Graeme Hunter/BBC/BBC Scotland/Happy Tramp