It takes a special kind of love to move into the lodger's room in the attic while your wife makes hay with her fancy man in the master bedroom. But that was the peculiar domestic set-up at the conflicted heart of Hattie, the true - yes, true - story of Carry On comedy legend Hattie Jacques.

Ruth Jones certainly looked the part of Jacques, all twinkly eyes and comfortable cleavage, her sunny smile masking the frustration of a career cul-de-sac. 'I know my casting; I'm the frigid fat girl,' she complained, acknowledging her role as the nation's favourite chubby, a 1960s Dawn French, if you like.

But though she gave a good impression of warmth, Jones's Hattie strayed a touch too close to heartless bitch for this remarkable story to fully convince. The heart of the tale belonged to wronged husband John Le Mesurier, played by Robert Bathurst with just the right measure of unqualified love and ruffled dignity. 'He's too vague to be unhappy,' claimed Hattie, granting herself licence to cheat, but Bathurst's nuanced performance turned Le Mesurier's vagueness into a self-protective shield.

As a period piece Hattie worked superbly, its glimpses of Carry On film sets, with Marcia Warren scene-stealing as an embittered bit-parter ('I'm sick of this batty old lady s***') a diverting treat. But we didn't get enough of the self-esteem issues that bedevilled Jacques and led her to jeopardise a happy marriage by falling for a devilishly handsome wheeler dealer who made her squeal between the sheets. She fell rather too easily.

Desperate Romantic Aiden Turner certainly looked the part, all moody scowl and hairy chest, but his gor-blimey accent was comedy working class. 'I'm not a bit of rough!' he exploded but that's exactly how he came across, fine for a lusty leg-over but hardly a prospective long-term partner. Which was why Hattie kept her husband in the house to talk to, during the intervals between the sex olympics.

As I said, peculiar. It fell apart when Le Mesurier met a new love, though everyone remained remarkably civilised, and Hattie's bit of rough ultimately left her. It was all quietly sad and a noble attempt to tell a tricky tale. But I never quite fell for it.