The Motive and the Cue breaches the inviolable sanctity of the rehearsal room. The play, set in New York in 1964, follows John Gielgud’s efforts to direct the world’s biggest film star, Richard Burton, in Shakespeare’s most demanding play, Hamlet. A member of Gielgud’s company, Richard L. Sterne, recorded the process and his notes form the basis of Sam Mendes’s riveting production. The show is a must for anyone who works in the theatre or wants to. Directors, in particular, will relish the glimpse it offers into Gielgud’s approach to a uniquely demanding text and to a wayward superstar who was free to accept or to challenge the notes given during rehearsals.

Mark Gatiss wisely avoids reproducing Gielgud’s famous fluting voice and instead he gives us the spirit of the man – his donnish, poetic melancholy and his bashful, squinty-eyed fortitude. After each rehearsal he retreats, monk-like, to a bare hotel room where he confers with earnest young actors who seek his advice. They almost genuflect to him. Burton, by contrast, sprints off to a luxury suite where he carouses with Elizabeth Taylor and the Manhattan in-crowd. Bored, jealous and distracted, Taylor amuses herself by casually tormenting Burton. She threatens to start affairs with male models and she scolds him for wasting time on Gielgud’s production when he might launch a fresh show in London with herself as co-star. He ignores her casual cruelties and she responds by increasing their ferocity. These lovers rely on a shared relish for destructiveness to keep their romance alive. Why? They’ve conquered the world and their triumph has left them hollow, restless and dissatisfied. These are beautiful pen-portraits by writer Jack Thorne.

Designer Es Devlin uses simple but emphatically sumptuous effects. Soft, empty colours for the rehearsal space. Sea-calm azure for Gielgud’s scholarly room. Hot crimson for the Burton/Taylor boudoir. Johnny Flynn has the all-but-impossible task of playing Burton on stage. No make-up artist could recreate that ravaged proconsular scowl and Flynn’s voice gets nowhere near the Welshman’s sweetly murderous rumble. He looks a bit mundane, like Tom Parker Bowles being impersonated by Taron Egerton, but he conveys Burton’s energy and his demonic and unstable arrogance. When he shows up drunk and wrecks an entire day of rehearsal, he receives a brutal face slap from Janie Dee’s Eileen. Dee, like most of the supporting cast, is all but overlooked by the script because there isn’t enough stage time to do the material justice.

This isn’t just a great production but a wonderful learning opportunity. Opened up into a 12-part TV series it could work as a primer for this play and for others in the canon. A complete beginner would start watching the series knowing nothing about Hamlet and would gradually and effortlessly acquire as much expertise as an English professor. It’s worth doing some research in advance. The more you know about Hamlet and about the personalities on stage, the more you’ll love it.

Retrograde is a good old-fashioned history play. The writer, Ryan Calais Cameron, heaps every scene with conflict and churns out pacy, gripping dialogue. He probably writes fast. That’s how his character speak and the play rushes breathlessly through a crucial moment in the career of Sidney Poitier. We’re in the mid-1950s and the future Oscar-winner has been spotted by a TV producer but he has to convince Mr Parks, a brutal lawyer at NBC, that he has the charisma and the backbone to make it as a star. At a mid-morning conference, Parks plies the young actor with whisky and quizzes him about his day job in a Harlem restaurant. Then he invites Poitier to satirise the accent of the Bahamas where he was brought up. He plays along with these power games but then Parks raises the stakes. He wants to know about Poitier’s colleagues in the civil-rights movement and their communist affiliations. Any TV contract, he hints, will be conditional upon Poitier’s willingness to denounce his friends. Then Parks names his real target. Paul Robeson was already too big for any studio to silence and he was regarded by right-wingers as a genuine threat to America. The condemnation of another black performer would be a terrific achievement for Parks. That’s the deal. Will Poitier betray his ally and enjoy a fat pay cheque and a cosy career in movies?

It’s not hard to guess the outcome but the final twist is cleverly timed. Ivanno Jeremiah plays Poitier as a handsome, self-possessed youngster with a hint of street-smart steeliness. But only a hint. He’s too saintly, noble and pure-minded. Result, a hint of dullness. Parks (Daniel Lapaine) is a more damaged, evil and interesting type. A roaring drunk and a seething bigot, he shamelessly manipulates Poitier to advance his own career. Accidentally he’s the star of the show.