I went to Phantom of the Opera on Monday. I’d never seen it before.

Has this thing really been running for 21 years? Why?

Unlike many Phantom audience members who plan and save and look forward to their visits like a state occasion, I was still mooching around the new Primark in Oxford Street at 7.25 thinking the curtain was at 8, so despite a swift cab to the Haymarket I missed the opening moments.

This did give me an opportunity to stand at the back of the Circle for a couple of minutes and survey the two to three full rows of empty seats, giving the lie to the claim on Lloyd Webber’s Really Useful Group website that “In London there has never been a seat unsold” … well there were at least a hundred empty on Monday 14 May 2007, Andrew.

Watching the drama unfold, and seeing the stilted performances, you start wondering why it just isn’t the hottest ticket in the West End any more.

I looked up the original cast – Michael Crawford and the queenly Sarah Brightman (who I can’t stand anyway) of course, but also the almost as queenly Michael Ball, superb David Firth and pre-Fred Elliott John Savident heading an impressively well-experienced ensemble.

Contrast this with the current collection of just-out-of-drama-school hopefuls and regional-theatre-veteran-understudies and you begin to see the flaws.

The creaking you can hear isn’t just the 21-year-old stage machinery (although that’s noticeable enough) it’s the cramping of budgets to the point at which the production is as undercast as it is underlit.

Some of the performances are so two-dimensional that in their bejewelled costumes and powdered wigs, you’re reminded of a pack of playing cards: especially Wendy Ferguson, subtle as a heifer in her role as fading diva Carlotta Guidicelli, and Heather Jackson who plays Madame Giry the ballet mistress more stiffly than if she were an exceptionally arthritic Mrs Danvers in Rebecca during an unseasonably wet Cornish winter. You’d just want to burn the house down with her inside, the wood in her performance could only add to the blaze.

Not that the leading men are outstanding: Earl Carpenter has been playing the Phantom for nearly 1,000 performances. If his mannerisms were any more arch, he’d need scaffolding. Michael Xavier is a tuneful but unwashed Raoul, more Che in Evita than a suave French Vicomte, and his darting stage moves in odd directions unrelated to the motives of his character made me wonder if he had Attention Deficit Disorder.

I certainly did in the second half when most of the tunes are re-hashes of the stuff you heard before the interval, and the plot descends firstly into the bowels of the opera house and then into … well, bowels really covers it.

This was the first night of the “new Christine”, although I couldn’t tell you which one I saw except to say she was shrewish and dark. The role is now being shared equally four performances a week between Leila Benn Harris and Robyn North. This is ostensibly to make audiences feel they are not getting the “alternate Christine” on any given night or matinee.

Since both performers are modestly experienced for West End headliners – Ms Benn Harris having understudied the one-number Mistress in Evita, Ms North most recently ‘touring with Shane Richie’, you could say it’s Alternate Christine EVERY night.

Who thought I’d ever pine for Sarah Brightman.