Stefano Massini’s play opens with a man in a frock-coat reaching New York after six weeks at sea. The year is 1844 and young Henry Lehman has just emigrated from Bavaria to make his fortune. He started modestly with a general store in Montgomery, Alabama, serving local farmers. When wildfires destroyed the cotton crop on which the community relied, Lehman’s business ought to have failed but he saw his opportunity. Whatever possessions the farmers had lost they would have to purchase again. From him. He was joined by his brothers, Manny and Mayer, and they invented the profession of brokerage, ‘middle-men’ they called themselves, buying raw cotton from farmers and selling it on to the clothing factories. The Civil War brought fresh destruction and fresh opportunities. Manny Lehman applied to the governor of Alabama for public funds to rebuild the shattered state. Lehman Brothers became a bank and it remained a family business until the crash of October 1929 when it was saved from liquidation by outside investors.

The first two acts of this play are done with extraordinary power and simplicity. Designer Es Devlin places the actors in a glass-walled office, which occupies two thirds of the stage and makes the Lyttelton’s unwieldy dimensions manageable. The office is slightly raised, like an altar, and it turns slowly on its axis to indicate a shift of time or location. The rear wall is a wraparound screen that bears projected images of the cotton fields, of the Civil War, of the rolling Atlantic, of the incipient towers rising on the New York foreshore at the start of the 20th century. The visual aesthetic is spare and frugal. Black and grey are the dominant colours of the stage furnishings and this palette is matched by the Lehman brothers’ dark Victorian suits, which they wear throughout the show.

Adam Godley, Ben Miles and Simon Russell Beale play dozens of roles as the family expands, grows rich, and passes its secrets on to the next generation. The virtuosity of the three actors creates more than just charm, intimacy and humour. There’s a kind of theatrical magicianship on display. Imagine an evening of fairy tales being told around the fireside by your three favourite uncles. The show’s great formal achievement is to set out an intelligible relationship between the motions of history and the gossipy, messy reality of family affairs. This is done with two straightforward visual effects. A small space on the stage where vast decisions are made, and beyond that space a world that has to respond to those vast decisions.

The final act covers the second half of the 20th century when the bank passed out of family control and was finally wiped out by the chaotic market conditions of September 2008. Inevitably, these events are less engaging to watch because the Lehmans themselves have withdrawn from the story and the firm is just a cash cow to be fought over by asset-strippers. And at 210 minutes the production is longer than perfection would demand. There are two intervals and the show includes a couple of dream sequences whose vivid colorations conflict with the purer visual aesthetic of the main action.

But I doubt if many of the press-night crowd would have agreed with these quibbles. At the curtain call the National’s concrete spurs seemed to thrum in harmony with the applause. This is a rare kind of triumph in the theatre, a show that could run for as long as the actors want to play it.

Knights of the Rose, at the Arts, is a soft-rock musical featuring a pick-and-mix selection of hits by 1980s has-beens. The medieval storyline involves strapping warriors in scratchy tights preparing to fight the mighty empire of Avalon while their swooning womenfolk prattle in olde Englishe. ‘Accursed be he who first invented war,’ pouts a buxom princess while her boyfriend laces up his leather breeches. The dialogue is the main stumbling block. Entire speeches from Shakespeare’s Roman plays are parachuted into the text alongside poems by Blake and Byron. The dances are uninspired and there are too many boy-on-boy routines involving camp knights exchanging lingering man hugs. Maybe that’s deliberate.

Half the cast have been chosen for their looks, the other half for their talent. This becomes evident as soon as the warbling begins: the prettiest players have the weakest voices and the less attractive ones sing beautifully. Matt Thorpe (Horatio) has an exquisitely tender voice and the sonorous bass of Adam Pearce (Aethelstan) is an amazing instrument to hear. The contribution of the women is dominated by their extraordinary waist-length hairdos. Half the Heidis of the Austrian Tyrol must have donated their tresses to this golden extravaganza. This isn’t a great show but it will appeal to committed head-bangers who have already seen Bat Out of Hell six times.