Silk, BBC One

There was a moment in last night’s Silk when a young solicitor turned up late for a trial. He was also an actor, he explained to his client’s counsel, and had to attend an audition. For a Head & Shoulders ad. The USP of Peter Moffat’s courtroom dramas is that, more than any writer since John Mortimer, he knows whereof he speaks. Having once been a barrister himself, the serpentine ins and outs of chambers, the politicking and skulduggery etc etc are his area of expertise. So you take it on trust that the events dramatised here are the truth and nothing but.

Thus a barrister furtively snorts coke at a chambers party. A pupil shoplifts a wig worth north of a grand. And a solicitor moonlights as an actor. If you say so, m’lud. As he explained to Adam Sweeting on theartsdesk, Moffat sees Silk as a belated chance to unburden himself of all the stories of the Bar dammed up inside him since Channel 4 didn’t commission a second series of North Square. This stuff happens. That’s the claim.

If there is a problem with Silk – and there definitely is - it’s the usual one that infects all television dramas, from Lip Service to Spooks. Take the two pupils attached to the two main barristers. One turns up on his first day with his tousled telly hair stuffed into a beanie. Another has lately been deemed saucepot enough to have sex with a Tudor monarch (Natalie Dormer, pictured below with Tom Hughes). If these two catalogue models are trainee barristers then I’m the Lord Chief Justice. In this version of the Bar, everyone looks like they’ve just come from an audition. That’s because they have. Which begs an important question. Whose version of legal reality are you inclined to believe? The casting director doesn't make the writer look like a credible witness.

So anyway, Silk is basically South Square. Same set-up, same characters, in one case even same cast. Chambers are still run by a wily hardnut of a clerk, played this time round by Neil Stuke. And once more there’s an ambitious, overworked female barrister (Martha Costelloe, played by Maxine Peake) fighting hard for preferment in a system which favours chaps: “245 women silks ever!” said Stuke to no one in particular. “You’ve got to respect a statistic like that.” You’ve certainly got to crowbar it into the script, anyway.

Peake, an actress with both feet planted in the world as you know it, excellently keeps as close to real as the script allows: fiery, committed, but also knackered and vulnerable. Meanwhile, opening the batting for the phallocracy is Clive (Rupert Penry-Jones, formerly of North Square), from the Dick Dastardly school for unreconstructed shits. All he’s missing is some moustachios to twirl. “Stop saying ‘tops’ like you’re someone normal, Clive,” Martha advised like a proper stroppy northern class warrior. “You went to Harrow.”  That’s telling him. And us.

There was a lot of that sort of exposition. This being a first episode, Moffat introduced a novice figure called Nick (Hughes) who knows nothing and to whom, therefore, things Must Be Spelled Out. He’s basically the show’s audience rep. Unlike an audience though, Nick’s meant to have a degree in law, so it’s remarkable quite how much does have to be spelled out. “What part of the phrase ‘Innocent until proved guilty’ are you not familiar with?” he was very nearly asked. Not that he’s necessarily the bluntest tool in the box. “How old are you?” Nick asked Martha. “Thirty-five,” she said. “How long have you been that for?” Smart repartee, but would a pupil aged 21 really be so cheeky on day one without getting a clip round the ear?

Silk feels most grounded when it puts itself in the hands of courtroom ritual and its inherently dramatic structure. Here characters must talk to one another rather than to the audience. The two court cases in this episode neatly crystallised the defence barrister’s dilemma: Martha lost a case for a defendant whose innocence she instinctively believed in, and managed to acquit a career criminal she intensely disliked. For the rest, Silk is working overtime to get your attention. Fur flies, glass breaks (twice, for good measure) and Penry-Jones tumbles downstairs. All in a day’s drama. “First impressions,” advised Martha. “Make them like you.” This juror is still out.

• Watch Silk on BBC iPlayer