Nina Raine’s new play deals with consenting to sex, both in the way a barrister questions a complainant in court and how he behaves in his own marital bed. It portrays how far we blur the boundaries of behaviour, treating each other and witnesses and our families remarkably the same. The tricks of cross-examination and the need to challenge whatever the other side says can all too easily be brought into the home.

The action is set on a large stage, banks of seats on either side, as if we were spectators watching sport in an arena. There are two couples at the heart of the play. Ed (Ben Chaplin) is a defence criminal barrister; his wife Kittty (Anna Maxwell Maritn) is a publisher who has given up her job to have a child which she hopes will be her first and last. Their good friends Jake (Adam James) and Rachel (Priyanga Burford) both criminal barristers and already parents have come round to toast the new baby boy. He is apparently played by Nina Raine’s own child. With a real baby also on stage in Jez Butterworth’s The Ferryman this is looking like a ‘must have’ for theatrical verisimilitude.

Ed and Jake talk about their cases, describing them in the first person (‘I’ve been raping pensioners’). Each married couple act happy at first, but in the course of the play, each will have a crisis in their relationship thanks to the husband’s infidelity.

In addition, there are two unmarried characters both of whom are desperate to have children: Zara, a jobbing actress (Daisy Haggard) and Tim (Pip Carter) who prosecutes in the rape case where Ed is defending. Tim has an accent which is as posh as his chambers (‘they take all the fraud cases’) but he comes over as boring and awkward. It thus seems odd when a man they all patronise is both treated as a friend and as suitable to fix up with Zara.

The brilliant moments come largely in the first act. Tim hesitantly tries to introduce himself to the rape complainant, Gayle (Heather Craney). He is halfway through describing why the case is delayed when she has to ask ‘who are you?’ Predictably she cannot understand why the defendant gets to have his own lawyer and she doesn’t. Ed’s cross-examination is masterly and commanding but also full of assertions and words that Gayle does not understand. He delivers it in a tone of voice which is quite different from his conversational accent. It is as if he has stepped up a rung in the class ladder by virtue of his role in court. Ed explains his attitude to lay clients as follows: ‘We’re not them! That’s why we’re paid to argue for them – because they can’t string two f***ing words together’. He is proud of his own lack of empathy though it hurts Kitty that he will say ‘I apologise’ but not ‘I am sorry.’ There is a great dialogue between Ed and Tim. It starts with both of them explaining effective advocacy to Zara who is auditioning for a part. The men then turn on one other: Tim cross-examines Ed on the basis that he is really there to flirt with Zara; in response Ed cross-examines Tim on the basis that he fancies Kitty. They’d already carried on their court battle to social occasions (‘She was a complete pisshead who kept changing her story’/’You f***ing excluded the fact that she knew he had previous for assault’). I can’t say how much the lay members of the audience appreciated all the subtleties in these scenes but if you do, they are a treat.

The men’s heartlessness in court is mirrored in their lack of guilt about their own adultery – although they both burst into tears when their wives order them to leave. Rachel’s suspicions had been aroused when she managed to read certain texts on her husband’s phone. Jake is one of nature’s aggressors and he dismisses the texts as a ‘joke’. He had just been ‘arsing around’ with a female pupil in chambers. No one says that it might not be appropriate for a married tenant to exchange erotic texts with a pupil. Good alpha male that Jake is, he cannot even remember the pupil’s name the next day.

The play is less strong when it comes to crises between the couples. Raine has a habit of ending scenes when it feels as if one is only ¾ of the way to the emotional climax. Act one ends with a coup de theatre which looks as if it is going to bring to a head the moral issue about how barristers operate. Then it doesn’t. Ed, Jake, Kitty and the witness Gayle are the strongest characters; the others are much less well drawn. The resolution of the two marital quarrels feels a bit unconvincing. However, a very fine cast carry you along, even when they have to fill in the motivation that the playwright fails to provide.

Sitting in the front row, I could not help noticing that the men were wearing collarless shirts but not a barrister’s detachable collar shirt. When I mentioned this to the person to my right, he said, in respect of Tim’s costume: ‘By the way, I thought barristers didn’t wear brown shoes.’