You see it every night in the theatre. People turn up insisting that you are in their seats only to discover, after a run-in with the ushers, that their seats are in the circle, not the stalls, or for Wednesday night, not for tonight, which happens to be Tuesday. But only critics, it seems, turn up for the wrong show altogether.

The most astounding example of this is surely the confession of Benedict Nightingale in The Times yesterday that he went all the way to Sibiu in Transylvania to preview Silviu Purcarete's production of Gulliver's Travels which opens tonight at the Edinburgh Festival - and found himself watching a Shakespearean mash-up with Hamlet chasing Bottom round the stage instead.

Well, at least he got to Sibiu, something of a miracle if Ben's own amusingly Pooterish accounts of his disorganisational abilities are to be believed. Nothing daunted, he watched Gulliver's Travels on DVDs, talked to the director, and cobbled together a fairly decent feature. And presumably sampled the delights, if there are any, of downtown Sibiu.

The escapade reminds me of Paul Taylor going to the Arts Theatre, Cambridge, instead of the Cambridge Theatre, London (or was it the other way round?) and of Clive James sitting through the first act of Othello at the Royal Shakespeare Theatre in Stratford-upon-Avon and wondering what on earth it had to do with Les Liasons Dangeureuses, which he was supposed to be seeing across the road in The Other Place.

And then there was the infamous case of Toby Young who, on starting a stint as theatre critic of The Spectator, admitted that he didn't know where the National Theatre was. It's funny, though, how you can get your theatres muddled up. I have to sit and think a minute still when I'm going to the Duchess to make sure I'm not going to the Duke of York's. And I'm never quite sure which is the Lyric and which the Apollo till I actually arrive in the middle of Shaftesbury Avenue. And is the Vaudeville before the Adelphi or after it when you enter the Strand from the Charing Cross end?

It was obvious last night with crowds milling around for the London premiere of Noel Coward's Volcano, a damp squib of a play that doesn't really sound like Noel Coward at all, even if it is a piece that might have shocked Rattigan's Aunt Edna. Make that Aunt Etna.

The lighting rig actually shook a bit when the volcano erupted, and you could almost see the stage manager giving the wobbly set a bit of a push so that Jenny Seagrove's collection of shells fell to the ground. The party of ex-pats make a trip to the volcano's edge and return with sore backs and aching limbs, and audiences might wonder what all the fuss is about. I can assure them that while the actors' moans, groans and physical jerks are a little under-researched, they are right to be feeling uncomfortable, and not just because they've been sitting on donkeys.

I once went to the top of Etna on Sicily and peered into the quietly bubbling crater. It was an astonishing sight, and an astonishing walk, and I'd followed the advice of taking a thick jumper for the descent, as the climate suddenly changes from broiling hot to freezing cold. And as with all erupting volcanoes, the downward path of flaking black lava is difficult to negotiate, and it is very hard to remain upright, let alone keep your balance. Hence the aches and pains later on.

That lava path is represented on the Vaudeville setting with what looks like a pair of giant baked caterpillars, or crusty foam sea urchins. I can see the argument of this unknown play - the same director, Roy Marsden, gave the piece its world premiere at Westcliff twelve years ago - being like something of Tennessee Williams, though without the florid, exotic language of either heart or soul. But it doesn't seem to me on this occasion that Marsden's cast fully inhabit the characters, sketching stereotypes and not always the right ones.

Jason Durr as Guy Littleton, for instance, comes on like far too obvious a Lothario to have any subtle, ingratiating charm, which was the secret of the writer Ian Fleming, the model for the role. And everyone in a Noel Coward play has to look stylish in some way. Not one actor on the stage looks stylish in any way whatsoever.

There are always consolations with a Bill Kenwright production, though, such as drinks and sandwiches in the interval. And last night, critics were given the additional bonus of a magnificent picture book, The Treasures of Noel Coward, written and compiled by the tireless Barry Day, full of rare photographs and detachable memorabilia, such as posters and programmes, letters and birthday cards and even lyrics ("I've been to a marvellous party") written in Coward's unremarkable scrawl on lined exercise book paper.

If you'd gone to the Adelphi next door by mistake you'd not have come away with so much as a mouldy pork pie of dubious composition. On the other hand, you would have seen two fabulous performances by Imelda Staunton and Michael Ball in Sweeney Todd, which is entering the last month of its run before making way for The Bodyguard. And after my review of Volcano I'll probably need one.