Mum, BBC Two, series 3 review - welcome last hurrah for adult family sitcom

It is a cliché that never grows old. From Fawlty Towers via The Office all the way through to (so we are told) Fleabag, a great half-hour comedy that bows out after two series cements its place in the pantheon by ensuring posterity wants more. Twelve episodes seems to be the platonic ideal of the perfectly proportioned sitcom.

When Stefan Golaszewski’s Mum (BBC Two) ended last time round there was thus a case for stopping there. It finished on a moment of such exquisitely subtle optimism. Parting from Cathy (Lesley Manville) and her daft coterie would have been a sweet sorrow that made excellent sense.

But here Mum is, back for a third series, and of course that’s great news. Because it somehow didn’t win any Baftas, perhaps it will this time round instead. The first episode suggests no drop in quality even though the action, such as it is, is no longer confined to Cathy’s suburban terraced home. The gang have gathered instead for six days in a vast home in Kent, which Pauline (played with pin-sharp passive aggression by Dorothy Atkinson) has rented for a week in order to flaunt her newly acquired riches after a divorce settlement.

Pauline is a glorious monster who flagrantly continues to beggar belief with her scorching snobbery and almost tragic insecurity. In this episode she couldn't stop boasting about the house’s many accoutrements, like an estate agent who’d swallowed a wasp's nest. For the moment in her seething rage she seems to have forgotten that she prefers her beta-bloke Derek (Ross Boatman) to exhibit his rough and tough side. Instead he was thrilled to have discovered a station called Radio 4 where they play no music and no one phones in.Meanwhile Cathy and Michael (Peter Mullan) are behaving like a couple of teens keeping their new love under wraps from Jason (Sam Swainsbury), Cathy's man child whose brooding antagonism suggests an unconscious Oedipal loathing for a usurping rival that he dare not acknowledge. Poor thick Kelly (Lisa McGrillis) was even less adept at shrouding her feelings. Her asking-about-pregnancy-for-a-friend scene with Cathy was a thing of tender touching beauty.

Mum somehow manages to be two comedies in one: a parade of grotesques rub up against a pair of superhumanly kind and tolerant people who barely make you laugh at all. How can they all co-exist on the same canvas? Well, Dickens managed it. Mike Leigh is the more immediate forebear, the connection made overt by the presence his most regular collaborator in Manville.

Golaszewski uses the rhythms of sitcom to do his own thing. His half-hour playlets put observation above plot, which edges along at a glacial pace. You long for things to happen – births, marriages, deaths, even a comeuppance for Pauline – but it would be unwise to expect anything. This series, though covering a week rather than a year, shows no sign that it intends to accelerate. Mum's still the word.

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@JasperRees