John Mortimer is not alone among contemporary playwrights in being at his best in his one-act plays. The same is true of writers as diverse as Ionesco and Peter Shaffer but for very different reasons. With Mr. Mortimer it is not an inability to sustain the development of a character over three acts—he does that quite well with Sam Turner in Two Stars for Comfort—but his plot nearly always depends on a narrative structure very much like that of an anecdote. The pattern is a simple one and could easily be spoiled by over-elaboration. The murderer is reprieved because the barrister, so talkative in the cell, becomes too tongue-tied to defend him. The private detective who can find no evidence against the woman he is shadowing starts by dating her and ends by proposing to her. The lunch-hour lovers get so involved in arguing about the...