But the breadth of what is on offer has been derided by, among others, the playwright Alan Ayckbourn - who railed against "musicals, musicals, musicals".
At the last count, there were 24 musicals to seven straight plays in the West End.
Unsurprisingly Ian, a judge on the BBC's hugely popular search for a star for the Sound of Music, is unrepentant.
He blames market forces, and says that being engaged in a high risk commercial venture, theatre producers have to pick shows which they think they can at least break even on.
But he also says there are "fabulous plays", particularly The View from the Bridge with Ken Stott which opened earlier this month.
Ayckbourn turned his back on the West End to protest against the merciless advance of the singing and dancing show - and Hollywood stars in lead roles who, he said, disappoint audiences.
Plays next?
Ian acknowledges the decision is increasingly based on "having to cast the poster".
"Unknown pieces with unknown actors are very difficult to sell just now," he explains.
However, Ian - once an understudy for Cliff Richard and David Cassidy himself - was able to cast unknowns in Grease, using the same TV talent show formula of the Sound of Music.
He points to the Saturday night success of shows like Any Dream Will Do, which cast Joseph, as a large part of the success in the current crop of musicals.
So could the TV formula work for well-known plays? Shakespeare, perhaps?
"I don't think people would engage in the same way," says Ian. "The reason they are watching is because everyone has an opinion on someone singing a song. It's easier to vote for people singing a song, than the nuances of an acting scene."
"I think they work well, these programmes, when it is a role the public know well. I think they could have great input into who Annie should be."
Annie is not yet on the cards, but Ian's attention is on two new shows for 2009 - and they are both musicals.
He is bringing a touring production of Flashdance to the West End and a stage version of Xanadu is in the pipeline.
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