This is a play that opens with dark mourning, a flicker of candles, solemn music and the tolling of a royal death knell. Not the sort of play you’d treat your grandmother to, if you’re (say) Prince William. But for almost everyone else, it’s a must-see, says Katie Jarvis

“To state the matter shortly, the sovereign has, under a constitutional monarchy such as ours, three rights – the right to be consulted, the right to encourage, the right to warn. And a king of great sense and sagacity would want no others.” William Bagehot, The English Constitution

This is a review with two diametrically opposed pieces of advice. The first piece of advice is aimed at two readers only – Her Majesty, Queen Elizabeth II and Prince Charles (and may I say, ‘A humble welcome to this review, your Royal Highnesses’). Whatever you do – gin/sherry-drinking; throwing sticks for corgis; talking to plants; writing letters to Government ministers about intellectually dishonest badger-lovers, etc – please do do it. But don’t, whatever you do, go and see this play.

But to the other 63,742,975 people currently living in the UK (or to however many of you who are reading; (honestly – should be a lot)), do go and see it! This play by Mike Bartlett is funny, imaginative, philosophical, engaging, clever, relevant. It’s not utterly brilliant (just quite brilliant) – we’ll come onto that – but it’s as entertaining and challenging a night in the theatre as I’ve enjoyed for a long time.

So I’m not giving anything away by telling you that the curtains open to the death of Queen Elizabeth II (and to beautiful music; I loved the music). The title kind of gives this away.

And onto the stage come the mourning royals, beautifully outlined for us in mostly blank verse – a little bit Hamlet; a little bit Macbeth; a little bit history plays. In pithy meters of five (and sometimes jumping in with both) feet, the excellent Robert Powell (while looking nothing like Charles but often sounding redolent) conveys the new monarch’s loneliness, his conflicting thoughts, his deep morality (“We’ll find no dignity in cov’ring up/ The way we feel.”)

They’re all there: a steely, determined (not un-Lady-Macbethian) Kate (her gift to us is ‘fashion’ – now there’s a great parody); Harry, who longs to shop in Sainsbury’s and eat kebabs (“I might head off if that’s OK” is an innocuous line until hilarious juxtaposed with others’ metrical phraseology); serious William; a Welsh Labour PM; and a two-faced Tory leader of the opposition, among them.

But the new King comes unstuck before he’s even crowned. The Government wants to push through an act restraining the press. (Quite how it will restrain is never revealed. But a look at today’s coverage of Brexit gives motive aplenty.) The King is adamant. This law would irrevocably harm democracy! He will not give token (but suddenly crucial) royal assent.

Oh, what a delicious irony. A man who has suffered more than almost anyone at the hands of the British press; a man whose wife would surely rise from her grave at the thought of him defending the media wolves…; a man who – one might say – unwisely challenged democracy with his under-the-cover letters to Tony Blair. This one man with so much to lose from gutter reporters is the one man who stands up for the media.

With disastrous results.

There’s so much to say about this play that’s good; fantastic. So many great, dodgy lines. “You look like you’ve been raped by Primark” is among the banter “very ginger” Harry shares with his friends. “You come across really badly on TV,” his new girlfriend, Jess (a St Martins student, nevertheless studying the relationship between Islam and pornography), tells him. And there are some delicious political digs about friendships with newspaper editors and gifts of horses. (Lol, as David Cameron would air-kiss.)

It is such a thought-provoking, gripping romp. My only gripe – maybe I noticed it unnecessarily – was around the blank verse. Arresting it might have been, but, for me, it drew attention to a gap in language. Charles is an empty vessel, a Spitting Image puppet, a simulation of the outer skin with nothing in the heart. Shakespeare created clichés; Bartlett, despite his brilliance elsewhere, uses them.

Nevertheless. This is a play that reminds us what theatre, at best, is all about. It tells a story; it makes us think; it shows us our own age, our own future, on a stage. It entertains and it provokes us in the most excellent of ways. Most of us, that is. Though not, of course, you, Your Majesty.

February 29-Saturday, March 5, Everyman Theatre, 7-10 Regent St, Cheltenham GL50 1HQ, 01242 572573; www.everymantheatre.org.uk