As a play that doggedly refuses to bare its teeth, The Lion in Winter is more like a lambkin in spring. James Goldman’s 1966 Broadway play was a flop at the time, but the title still resonates because of the movie.

So, on paper at least, this sounded like a good seasonal bet for Trevor Nunn’s final throw in his Haymarket tenure as artistic director: a solid historical drama with all the trimmings and the star power of Robert Lindsay as the gruff, Lear-like Henry II and Joanna Lumley as his imprisoned queen.

Instead, we seem to have run into a diluted medieval version of an Alan Ayckbourn play, set around the Christmas tree in Henry’s French chateau, where family divisions and the future of the king’s occupation of France are batted around like, well, a whole lot of balls.

“It’s 1183 – and we are still barbarians!” You could have fooled me. At least Peter O'Toole tears into the role on screen like a demented savage with a cruel streak; Lindsay opts for the sardonic approach and, despite deploying his always impressive full vocal range, he astonishes me most by being so boring.

He’s kept Eleanor of Aquitaine, ten years his senior, in prison for a decade, though Miss Lumley, fragrantly elegant as ever, looks as though she’s just stopped by from a Bond Street beauty parlour en route to a fancy dress competition.

The court has been assembled – though we don’t see any flunkeys or trumpeters – to thrash out the future of the dynasty, which involves Henry’s three gormless sons (two of whom, historically, Richard Lionheart and John, would eventually succeed), King Philip II of France (Rory Fleck-Byrne), who is the son of Eleanor’s former husband, Louis VII, and Philip’s half-sister, Alais (Sonya Cassidy), who is Henry’s mistress.

What happens? Very little, and the play, which bristles with a job lot of funny lines that aren’t actually funny, expires slowly around its perpetrators until it stops in a fractious stalemate. By which time one has rather tired of admiring Stephen Brimson Lewis’s beautiful set of receding grey arches and seasonal decorations.

Mind you, the evening did not start well in offering a view of the inert stone effigies of Henry and Eleanor followed by several projected paragraphs of historical scene-setting. Come on, folks, this is a theatre, not a lecture hall: if you can’t act it, cut it.

The best you can say of Goldman (brother of novelist William), who died in 1998, is that he had the good grace to go on from this to write the libretto for Sondheim’s Follies and the screenplay of Nicholas and Alexandra.

Robert Lindsay electrified Martin Sherman’s Onassis with his performance as the monstrous Greek shipping magnate, but seems in no mood to pull the stops out here. And Joanna Lumley doesn’t so much perform as deliver a judicious selection of poses and pronouncements that seem strangely unequal to her brittle talent.