In Henry IV, Part 2, Shakespeare has the monarch, sleep-deprived and schemed against, lament that "Uneasy lies the head that wears a crown". In his eponymous play, his son, Henry V, also marvels at the burdens of office. "What infinite heart's ease/ Must kings neglect, that private men enjoy."
It is to the credit of this record-breaking production, the latest and most-seen in the NT Live* series, that it also conveys the private griefs of being the monarch, while remaining supremely watchable and, very often, very funny.
Written by Peter Morgan, whose script for the film The Queen gave Mirren the defining role of her late career, the play uses the weekly private audiences between Elizabeth II and her prime ministers (12 so far) as a setting in which to ruminate on recent history, affairs of state, palace protocol, constitutional convention and a host of other matters.
It's quite an achievement to maintain audience interest for more than two hours in an extremely formal interaction which is, by its very nature, low on tension and drama.
But, as Morgan himself remarks in an entertaining interval featurette, it is in such formal settings that we reveal ourselves the most: our everyday conversation is carelessly and inattentively undertaken.
The play ushers seven of those 12 PMs (Major, Churchill, Wilson, Brown, Eden, Thatcher and, briefly, Callaghan; Tony Blair, who had a longer audience in The Queen, is conspicuous by his absence) into the royal presence at Buckingham Palace or Balmoral.
The depiction of the guests is variously successful: Gwynne nails Thatcher's voice, but she's too tall for the role and has too much of the gunslinger's swagger about her; Fox's command of Churchill's vowels makes us forget that he lacks the great man's jowls. Meanwhile, McCabe's Harold Wilson is done with such glee that it's easy to forgive some of the character's coarser improbabilities.
The play rests, of course, on the breathtaking range and command of Mirren's performance. She matches several "how did they do that?" costume and wig changes with transformations of her own: when the 67-year-old becomes a still-uncrowned 25-year-old, there is an audible gasp.
But, for all its dry wit, the film is suffused with a nostalgic, even elegiac, glow: cleverly Morgan externalises the Queen's private anxieties, locating them in a 12-year-old self (Nell Williams), who shows up from time to time on a bicycle or in Girl Guide uniform. Only with young Elizabeth can the older one drop her guard and, when she does, it's magic.
* NT Live is a project of London's National Theatre in which productions are filmed and broadcast in real time to cinemas on both sides of the Atlantic. We get them here on hard drive a few weeks later.
Cast: Helen Mirren, Paul Ritter, Nathaniel Parker, Richard McCabe, Edward Fox, Michael Elwyn, Haydn Gwynne
Director: Stephen Daldry
Running time: 145 mins
Verdict: Majestic Mirren