Neurodiversity is not an obvious subject for a sitcom. But such misgivings are quick to recede during the charming second season of Austin (BBC One, Friday, 10.40pm), the Australian-British comedy about an autistic Australian man who discovers that his father is the British author of twee children’s books.Series one saw Austin (Michael Theo) travel from Canberra to London to bond with the dad he never knew (Ben Miller, who, it turns out, is not the same person as Rob Brydon) – with consequences that are by turns sweet, life-affirming and unspeakably toe-curling.In real life, Theo is neurodivergent, and his portrayal of Austin feels well-judged. There are loads of laughs, though never at the character’s expense. At the same time, the series neither condescends to nor infantilises Austin. He is a fully realised person – caring and thoughtful, but a bit grumpy and self-centred too.The humour is gentle and gently barbed. The stuffy Julian (Miller) is semi-estranged from his wife Ingrid (Sally Phillips), still absorbing the news that her then-boyfriend had a fling with Australian Mel (Gia Carides) in 1994. She sees this as an opportunity to move on from a moribund marriage and has relocated to the garden shed – to the disbelief of Julian, who is baffled as to why life can’t just carry on as before.But there’s a new bombshell as this second season gets under way. SPOILER ALERT: Doubt has been cast on Austin’s parentage after a DNA test reveals he and Julian may not actually be related. Was it all a tragic misunderstanding?This does not align with Mel’s recollections in Australia: she is quite certain that the timeline of her fling with Julian tracks with her son’s birth. It also leaves Julian at sea: he was initially horrified to discover he had a secret child, but has since grown close to Austin. Was their bond built on an error at a DNA lab? The truth of the situation is revealed in a hilarious journey to Northampton where Julian, Ingrid and Austin spectacularly gatecrash the lives of an unsuspecting family and then exit stage left, leaving a figurative smoking wreck.Austin is part of a new genre of sitcom that leans into the cringier elements of everyday life – you laugh but inside you’re curling up with embarrassment. There are many other examples – Sharon Horgan’s Motherland (and spin-off, Amandaland) and Daisy May Cooper’s Am I Being Unreasonable, for instance.All these shows share an aversion to punchlines and a preference for wry gags, strung together by an understated soundtrack (lots of dry piano tinklings). But if that’s a formula, then it is followed to perfection here in a series that is a quiet joy from beginning to end.