Robert Moses, who largely landscaped metropolitan New York, shared the name of a famous biblical character. Although there, as David Hare’s new play makes vividly clear, the comparisons ended. The urban planner was a far more self-confident prophet and notably more insistent about his commandments being followed. As captured in Ralph Fiennes’ enthralling performance, the American Moses wouldn’t have delivered his instructions from a burning bush, but would have incinerated the entire landscape. Moses’s life encompassed 18 different US presidents, from Grover Cleveland to Ronald Reagan, but Hare focuses on two enclosed episodes. In 1926, he strong-arms New York governor Al Smith into agreeing two vast expressways that will connect the city to parks and beaches on Long Island; in 1955, he attempts to put a road through New York’s Washington Square Park, but is resisted by early versions of nimbyism and environmentalism. Hare once made a version of Henrik Ibsen’s The Master Builder, about an agonised old architect, and Straight Line Crazy feels a knowing homage to that play and Ibsen’s An Enemy of the People, in which the protagonist’s attempts to improve local lives make him a pariah; like him, Moses believes that he is always right and the majority wrong. To the extent that he is, Moses is generally known through Robert A Caro’s monumental 1974 biography, The Power Broker. Hare’s play has no declared relationship with that book (which isn’t even mentioned in the programme) but he has highly praised it in interviews, and there is a stylistic connection. Caro’s long, rhythmic lists of Moses’ projects and motivations sound echoed in riffs that punctuate the action. Dynamic, ideas-driven dialogue, though, makes the play crackle. In a long scene as strong as any Hare has written, Moses and Governor Smith – electrifyingly played by a cigar-sucking, homburg-doffing Danny Webb as a sort of American Churchill – duel over elected and unelected power, the rights of citizens to shape their city and Moses’ belief that areas may need to be ruined to improve them. The three-decade jump to the second act leaves a tangible Smith-shaped hole, and tension somewhat reduces, but Alisha Bailey and Siobhán Cullen impress as Moses’ employees who map cultural movements more astutely than he does. Fiennes’ most recent theatre appearances have been monologues: portraying the playwright in Hare’s Beat the Devil, a soliloquy about surviving Covid, and animating TS Eliot’s Four Quartets. Those solos demonstrated the actor’s remarkable control of voice and body and these skills are not diminished by now sharing the stage with 12 other actors. Often angling his body backwards to thicken his silhouette to the fuller-set Moses, Fiennes emphasises the man’s awkwardness in his skin to the extent of almost becoming a reverse Richard III. Nicholas Hytner’s populous production, with multi-location sets by Bob Crowley, continues the director’s trick, at his new venue, of somehow carrying on as if he has the budgets and resources previously available to him at the National. This is Hare’s most dramatically gripping and politically thoughtful play since The Absence of War three decades ago and provides another acting triumph for Fiennes which, in scenes where the urban monarch broods and rages over maps of his American kingdom, is a preview of the King Lear that is surely soon to come. At the Bridge theatre, London, until 18 June and broadcast by NT Live on 26 May