The Agent, Trafalgar Studios, London

On the tiniest details is trust founded or lost. Putting on his coat, the title character of Martin Wagner's play tells his assistant to book a table for three at "my usual" for a time less than a quarter of an hour away. One needs merely a grain of common sense to wonder: what if it's full? The agent will be out the door before he knows.

And wouldn't it be more natural to name the place? But I fear Wagner thinks the phrase typifies the talk of tough, curt men of power. Too harsh? Then consider that the agent plans to begin lunch at... noon. Children, labourers, the elderly and the incarcerated may lunch at 12, but, last time I looked, none of these was bargaining with publishers.

These points are but specks in a cloud of unknowing that hovers, grey and wet, over The Agent. We are asked to believe that a timid, clumsy writer has happened upon the agent in a compromising position, photographed him, and then blackmailed him into heavily promoting a plotless novel about miners. The publishers then outbid one another until the writer is offered an enormous advance. Writers whose senses have been corroded by rejection and spite may swallow this, but no one else will.

The dialogue of The Agent is as witless as its premise, and its hypocrisy is greater than both. Wagner may reckon that the authors of novels spurned by agents are numerous enough to provide him with an audience. He does not, therefore, suggest that these writers may have only themselves to blame.

And he takes care not to attack publishers, here presented as able to spot greatness where the agent could see only dross. In fact, it is publishers who are the villains of the book world – chasing imitations of last season's success, ignoring good authors and ideas, pressing fortunes on boring bureaucrats and imbecile celebrities, whose books the public shuns.

William Beck as the agent and Stephen Kennedy as the writer work hard, but to no avail, to supply (in Lesley Manning's production) the reality the author has not. Plays like this often contain a line that seems to spring from the writer's unconscious, in this case: "The greatest thing in life is to know the limitation of your talents." The thought is hardly original – Shaw expressed it in much the same words – but it is wise.

To 18 August (0870 060 6632; www.theambassadors.com)