It’s part three and we’ve reached May in this acutely tragi-funny look at a year in the life of widow Cathy (Lesley Manville). The weather is warming up and so is the romantic heat between Cathy and old friend Michael (Peter Mullan), who seems to be spending a lot of time at her house. Well, he’s always there when the cameras are there anyway.

The focus this week, however, is on raucous, gormless Kelly (Lisa McGrillis), the girlfriend of Cathy’s son Jason (Sam Swainsbury). Just as you think there is nobody as awful as Kelly her mother pitches up do outdo her own offspring in the rudeness stakes.

What could be 30 minutes of awkwardness and class mockery, however, actually does a sharp gear change half-way through. We get to discover why Kelly is the way she is by seeing the behaviour of her mother. And for once dignified, polite Cathy actually speaks her mind, making the situation better. At least temporarily.

There has been some grumbling recently about sitcoms that aren’t wall-to-wall laughs and Mum might fall into this category. But if you want traditional sitcom giggles you can get them here via Cathy's social climbing brother Derek (Ross Boatman) and his girlfriend Pauline (Dorothy Atkinson), who have muscled their way into the golf club and invested in over-expensive checked sports gear only to go and make an etiquette error of cataclysmic proportions. Their bourgeois balls-up is all a bit suburban Terry and June, but thanks to the writing of Stefan Golaszewski it is as beautifully observed as the rest of this series.

Mum, BBC2, Fridays, 10pm.

Review of Episode 1 here.

Review of Episode 2 here.