There’s no surer sign that you’re watching a piece of feelgood screen drama about well meaning working class folk than a karaoke scene. No episode of Linda Green was complete without Liza Tarbuck emoting with mike in hand as decent sorts supped pints around her. And now Steve Coogan is at it in Sunshine, a BBC1 three-parter about a gambling addict married to a loving wife.

Their sparky son provides occasional narration when he’s not being fed tall tales by grandad Bernard Hill, and life couldn’t be perkier and warmer, at least at this point in the tale. Doubtless things will get worse as Coogan’s character runs into real problems with his gambling, but right now it’s about as convincing a perspective on the perils of the betting shop as Pretty Woman is an accurate guide to the life of a prostitute.

Scripted by Craig Cash and Phil Mealey, it’s a story that’s all about sheen and doesn’t penetrate the amiable personas of any of its happy-go-lucky characters. It’s relentlessly pleasant, even when the story shifts to the Black Cat, an underground gambling den with a supposedly threatening boss figure who wouldn’t scare the blue rinse off a bishop’s mum.

The performances are as good as they can be allowing for the superficiality of the script. For a show where so much is at stake, there’s precious little feeling that much is amiss. That’ll change in the episodes to come, but the core issue is the tone of the writing, which just doesn’t bear the weight of its subject matter. I’m not insisting that it be grim and portentuous, but tonally Sunshine utterly fails to convince. A shame, since there’s serious talent involved in the show, in front of and behind the camera. Part of the problem has to be Craig Cash’s direction, which gives every scene equal weight and doesn’t have any sense of light and shade, other than an ill-fitting dialogue-free sequence set to opera at the end in which some of Coogan’s chickens start to come home to roost.

Going back to Linda Green, lightweight as it was it nevertheless got under the skin of its plucky heroine and as a consequence it was easy to feel moved by her predicaments. But Paul Abbott is an altogether more skilful writer than either of Sunshine’s. Some of the choices just seem ill-considered. The voiceover by the young son is too sugarsweet, and I can’t help feel he’ll be there to soften the edge of any potentially upsetting sequences, exactly those that a series that’s allegedly about gambling needs to have real impact.

Craig Cash started out on Royle Family, and underneath that show’s amiable portrayal of life in front of a telly was a perceptive depiction of intergenerational conflict. Now, I’m left wondering how much of the acuity of those scripts was down to Cash’s co-writer, Caroline Aherne. Maybe, just maybe, the next two parts of Sunshine will prove me wrong.