LAST NIGHT

In the second episode of Have Your Cake and Eat It (BBC1), the series' executive producer, Michael Wearing, took a small cameo role as Man at Spanish Hotel Bar and he performed his part most feelingly, turning with an indulgent smile as Sam and Alison finally succumbed to the powerful force between them (it looked like some kind of suction, given the clamp of their lips). Then again, this may just have been an involuntary expression of relief on the producer's part - infidelity being a rather more dependable commodity with the public than the heroic abstention the lovers had been attempting to maintain until then. They were in Spain to visit a fairground because Sam (rather gloriously, after all the mundane professionals we've had in previous Des Res dramas) was a roller-coaster architect, an occupation which, quite apart from the obvious ironies about life's ups and downs, also allowed for a stirring opening sequence in which a white-knuckle ride at Chessington was intercut with Sam and Alison's first night together. As a metaphor for the thrills of adulterous sex, this was very good - suggestive of apprehension mixed with elation and also of the way that physical momentum takes over at a critical point.

Since then, though, it has been difficult to shift the notion that Rob Heyland has some larger analogy in mind for his script. Certainly, the first two episodes seemed to be engineered on familiar fun-ride principles: a long, exciting ascent in part one, cranking enough energy into the storyline to sustain the run-out, and then a vertiginous drop in part two, in which revelation and confession were followed by much shrieking, tears, plate-flinging, car-crashing (his and hers) and name-calling. If the pattern was to be sustained, then parts three and four would involve sudden G-force-inducing twists and loops, followed by a last anti-climactic roll back to the place where we had started from.

And, sure enough, the very last frames of part two delivered the announcement that Alison was pregnant, something that Charlotte had declared a capital offence when taking Sam back, and you could barely tell up from down in the following hour. Sam went back to Alison, then - with some psychological plausibility, given that Sinead Cusack looks sexy even when tear-streaked and sobbing - started having a bit on the side with his wife as well. It had occurred to you several times that a man this billboard-faced had been unwise ever to embark on an infidelity, given that, every time he was asked a pertinent question, the words "Guilty Bastard" were transmitted in Morse code by his darting eyes. Alison soon read the signals but, astonishingly, Sam appeared to have pulled it off: "I have both the women I love and my children," he announced smugly at the beginning of part four.

There were a few twists left, naturally; the revelation of Alison's pregnancy (Charlotte helped her through labour, a funny scene in which the notorious rage of transition was delivered at the father's wife, rather than the father himself) and the first intimation that the avuncular barrister assisting Charlotte wanted to explore her briefs more fully. But, even so, things seemed to be decelerating safely to a stop. There were some pointed shots of Sam looking mildly let down, as if realising, for the first time, that all that endless queueing had led only to a transitory thrill. At which point, the two women pitched him out of the car, deciding, with the timing of synchronised swimmers, that three could play at that game. The final shot was a freeze-frame of Sam's stricken face, a sacrificial victim to a blend of ancient proverbial wisdom and gender politics. This delivered a certain vindictive satisfaction at the cost of abandoning all the drama's more provocative elements - the idea that a complicated emotional compromise might be better for all concerned than a bitter divorce. Naturally, we were happy that Charlotte could wipe the smile off her husband's face, but you had to wonder whether her younger children would also rejoice in Daddy's expulsion, however richly deserved it was.