King John (Rose Theatre, Kingston)

King John used to be prefixed with the words "the rarely performed" – but Trevor Nunn‘s production follows last year’s by James Dacre, both making a claim for the pertinence of the text. It’s a play of political vacillation, featuring changeable rulers that claim lofty convictions, then compromise; that pronounce their principles, then switch sides. Public faces that can soon be turned in private.

So, yeah, quite timely when we have a government that u-turns like a teenage joy-rider, Brexit campaigners that stamp and smear like children to aid their own careers, and Trump saying literally anything in his bid to become president. Not that Nunn’s production makes any of that explicit – we’re in full Medieval dress, with suspiciously clean, primary-coloured tunics and banners.

Still, the idea that politics is a playground is one that comes through loud and clear, especially in the lighter-footed, comic first half. That the second goes awry is a common complaint, and Nunn’s text includes additions from Shakespeare’s source material, The Troublesome Reign of King John; according to Nunn, the play otherwise appears to be "incomplete". This is not uncommon, a tradition begun somewhat controversially by John Barton (who also crafted The Wars of the Roses which Nunn recently staged in this same theatre) back in 1974. But as it lags towards the end, you wish Nunn had sliced more and augmented less.

Jamie Ballard is petulantly childish as King John: smirking and sarcastic towards the Catholic church (he pops out the words "the Pope" like a punchline), but lip-chewing, hand-wringingly wet when contemplating the nastier elements of war. It’s an excellent bit of casting, and a lively performance.

The spats between his mother Queen Elinor (an imperious Maggie Steed), and his sister-in-law Constance (Lisa Dillon) – who has a rival claim to the English crown in her young son Arthur – are snarled and catty. Dillon’s Constance is such an insufferable tiger mother and embarrassing scene-maker, that even when she loses her son she fails to win much sympathy.

Against a twisty plot of back-and-forths over war-and-peace, the righteously consistent Philip the Bastard – King John’s henchman – should be a welcome foil. But it’s a provocative part too, and while Howard Charles swaggers, and speaks his excoriating soliloquies with cheek-blubbering relish, he lacks mischief, too often coming across as just a bit shouty.

It’s a criticism that could be levelled elsewhere too. Although Nunn makes the machinations over who’s heir to the throne, and who’s loyal to the church, all clear and followable, the acting is at times over-inflated. A moment when King John is visited by various troublesome ghosts in a dream – an unwise addition to the Shakespeare – is pure ham.

But soft! What light through yonder TV-screen breaks? It is a live camera feed… How’s that for authenticity? It’s actually not a terrible conceit: public speeches are live-streamed to large screens, making explicit the connection with today’s media-trained politicians. But in this production, it looks very weird; the screens feel anachronistic, and not in a zingy way. And unforgivably, outside the speeches they mostly just show distracting literal photographs of the mise en scene: now a stained glass window, now a castle wall. It’s so basic.

The mind flicks to Ivo van Hove‘s sophisticated use of video in another recent Shakespeare-as-politics show, Kings of War, and the comparison does Nunn no favours; it’s like he read somewhere that screens would make it all modern and relevant and that. Actually, Nunn’s production elsewhere proves that you don’t need to strain to prove the play’s contemporary resonance: we get that, when it comes to politicians breaking promises, "twas ever thus, and will be."

King John runs at the Rose Theatre until 5 June.