Well, it’s okay, “what what,” but Alan Bennett’s dramatic anatomy of King George’s painful business of sitting on the throne proves a tough call in the West End. The play is hard to follow and the task of matching the historical story to contemporary application elusive.

It’s still a great pleasure to sit through, though I honestly don’t think that half the people in the audience understood what was going on. This in no way detracts from the brilliance of David Haig in the title role, making of old “Farmer George” a sympathetic buffoon with a bowel condition and a canny eye on the plotting politicians.

Was it porphyria – purple urine and blocked motions – or was it sheer frustration at political shenanigans with Pitt and Fox that drove the monarch mad and monstrous like King Lear in crinkly tights and tunic?

This was the defining role, twenty years ago (and in the subsequent film), of the late Nigel Hawthorne’s career; Haig, an outstanding character actor who still needs a sharper profile with the public, claims the part as his own, and finds fresh and fruity diversions within. He plays frustration better than anyone; and he’s effortlessly funny even when the play – oh dear, I wish it were -- isn’t.

Christopher Luscombe’s brisk and well-cast production hails from the Theatre Royal, Bath, and is a testament to that venue’s on-going creative and re-defining policy, a smack in the chops to most major regional reps while maintaining an eye on the commercial market.

Nicholas Hytner’s National Theatre production of 1991 – hey day, what larks -- opened with a golden staircase and a blast of Handel. Luscombe and designer Janet Bird cleverly modify this to a backdrop of gold leaf panels and an almost constant soundtrack of Handelian baroque decoration.

Across this colourful backdrop flit the royal household of Beatie Edney’s roly-poly Queen Charlotte, Christopher Keegan’s fleet and Christopher Biggins-like Prince Regent and William Belchambers’ neatly turned Duke of York.

The play becomes infinitely more interesting when it closes in on George’s supposed “lunacy” with bonkers advice and diagnosis from Madhav Sharma’s Dr Warren and Clive Francis’s incisive Dr Willis, though Thomas Wheatley keeps butting in with homespun philosophy as Lord Thurlow in a snowy white poodle wig.

It’s an enormously clever play, I now see, without being a very compelling one. But it’s a more than decent addition to the West End list, and we should be so lucky to have Alan Bennett still writing for the theatre when so many lesser writers of his generation, and after, turn up their noses at Shaftesbury Avenue.