The two rules of an Andrew Davies adaptation - and we all know them, especially the second - is that you maximise the humour and you turn up the sex. Davies is the greatest translator of literature into television working today, but his strengths are also his weaknesses. His humour can trivialise and his appreciation of the narrative possibilities of sex can, given sufficient licence by the original text, turn into monotonous bawdy. For my taste, the process that liberates a starchy, moralistic warhorse such as Middlemarch becomes too much of a good thing when applied to something as inherently libidinous as Moll Flanders.
Tipping the Velvet (Wednesdays, 9pm, BBC2), his latest luxury adaptation for the BBC, is not of a staid Victorian novel but a piece of contemporary queer fiction by Sarah Waters that happens to be set in Victorian times. It would have been interesting if he had reversed his normal methodology and turned down the incidences of sex, of which the text evidently provides a surfeit, but tried harder to take the characters seriously. Instead, Davies seems to find lesbians inherently hilarious.
Seeking a clear line through the text, he and his director, Geoffrey Sax, have made the episode in which the heroine, Nan Astley, joins the music hall as a drag king (a cross-dresser) set not only the visual style for the piece but its moral tone. Sex scenes are speeded up and intercut with flashes from Nan and Kitty's (her lover's) act. They are played against songs by Terry Davies that are smuttier than the era would have allowed ("Some they like it this way and some they like it that/Can anybody tell me where's my little Willy now?"). And everyone talks in double entendres.
Most of us have got over the meaning-shift that has occurred to the word "gay", but Davies twice lazily puts the adjective into his characters' mouths. "You seem so very gay and bold," says Nan to Kitty (Keeley Hawes). When they reach London, their impresario, Walter Bliss, welcomes them to the "gay metropolis". Then, showing them to their digs, he says, "You won't mind doubling up, I hope", and we cut away to the room, as if Sax is hoping for a reaction shot from the bed. The only double meaning I actually like is the title, which seems to refer both to what a gentleman does to his bowler when a lady passes and, well, cunnilingus.
By next week's instalment, the whole thing has become a silent-movie version of a picaresque romp. There is much use of Perils of Pauline contracting circles to cut between scenes. Realism thus abandoned, we watch Nan, dressed as a soldier, give blow jobs in alleyways to elderly gentlemen, none of whom notice the inescapable fact that she is a girl.
Next, she falls under the influence of a grotesque society dominatrix (Anna Chancellor), who has noticed. But she employs her to entertain her rich salon by attaching a dildo to her pants. At this point, a fascinating question seems about to be posed: is a lesbian only a lesbian when she has her hair cropped, dresses like a man and has a penis, or can society allow her to preserve her femininity? Sadly, the moment passes and the question is lost in the noisy decadence of the episode.
I hope the serial sobers down in episode three, for episode one, in which Nan realised her sexuality, was - until the vaudevillian stylisation took over - fresh, human and credible. Nan, who works in a seafood factory in Whitstable ("where the oysters come from", as she later says, having presumably seen Charlie's Aunt a few too many times), is associated with sea and sea salt. She smells, we are told suggestively, not like a herring but like a mermaid, and there is something exotic and magical about the woman as played by Rachel Stirling, as if her sexuality has separated her from her class and now she communes with more elemental forces.
But Waters is so keen to avoid her story becoming another whinge about minority oppression that the absence of raised eyebrows in Whitstable, theatreland and among London landladies to lesbianism adds to a general lack of credibility. The only opposition comes from Nan's sister Alice, who early on speaks pointedly of show folk - or is it lesbians? - as not leading "natural lives like us". But her reservations are discredited by the end of the first episode, when she confesses that she has finished with her boyfriend because "Tony likes men as much as girls". In Tipping the Velvet, everyone's sexuality is amusingly fluid.
From this fanciful premise, Davies has built, down to the arch voice-over, a gay version of his Moll Flanders in 1996. As in that, there is so much sex - and so much of it is treated so snickeringly - that the effect is not even tumescent. No offence to Rachel Stirling or any of the girls who strip, but for raunch give me any episode you choose of The Avengers - provided they star her mum, Diana Rigg.
Andrew Billen is a staff writer on the Times