91Èȱ¬

Graham Norton has presented the three previous highly successful 91Èȱ¬ One shows searching for a new musical-theatre star – How Do You Solve A Problem Like Maria?, Any Dream Will Do and I'd Do Anything. However, he thinks Over The Rainbow is far and away the most demanding yet for the contestants.

The hugely likable 46-year-old presenter, who also hosts the very popular Graham Norton Show on 91Èȱ¬ One, explains why he believes this show – looking for a young woman and a dog to star as Dorothy and Toto in a new West End production of The Wizard Of Oz – will be the most testing of all the musical-theatre talent hunts thus far.

"It's the biggest challenge we've ever set the public," asserts Graham, an enormous fan of the 1939 movie of The Wizard Of Oz that turned Judy Garland into a global star.

"It's the most difficult hurdle to get over. Dorothy is such an iconic role, and it's so difficult to get beyond the associations with Judy Garland – no one has ever come close."

For all that, Graham is delighted by the calibre of the performers who have already tried out for the part. Auditions have been held in Manchester, Glasgow, Cardiff, Belfast and London – and the best contestants will be sent through to 'Dorothy Farm' and then on to the live elimination shows.

"The standard is phenomenally high," enthuses the genial Graham, who in January last year made his West End debut as Albin in the musical La Cage Aux Folles.

"I'm really impressed by the overall level. Everyone who's gone through can really sing – it's quite extraordinary. We're now down to the last 50, and there is not a single dud among them."

He adds: "No one out of the final 110 was bad – they could all do it. Finding the best 50 was really hard. As we told some of them, 'I'm afraid you're not going to Dorothy Farm,' they would sob. We had to remind them: 'Look, you're really good. Thousands of people went for this and you got down to the last 100 or so!'"

The Dublin-born presenter was especially admiring of the younger entrants.

"We had a lot of 16-year-olds. I worried beforehand that they might not be able to handle it – I remember what I was like at 16 and I would never have been able to cope at that age. But I needn't have worried.

"We had call-backs at the Hackney Empire, which is a massive 2,000-seat theatre. These tiny girls were walking out on stage in this big, gaping cavern and saying, 'this is my dream,' before performing brilliantly. They were so self-possessed. They were just 12 when these shows started back in 2006, and now they're starring in them!".

According to Graham, the younger demographic on Over The Rainbow means that "The vibe on this show has been much nicer. Because a lot of older women auditioned to play Nancy, there was a much stronger whiff of despair on I'd Do Anything. If someone is 40, they may not have many more opportunities left to make it in musical theatre. But if someone is 17, it's much easier to say goodbye to them because you know they'll have hundreds more opportunities."

Graham goes on to list the traits that the three new panellists, music stars Charlotte Church, Sheila Hancock and John Partridge, and the lauded composer Lord Andrew Lloyd Webber, who oversees proceedings, are hoping to unearth in their Dorothy.

"The winner will require a great range of characteristics," says the presenter, who is also fronting 91Èȱ¬ One's coverage of the Eurovision Song Contest again this year.

"She will have to be innocent and vulnerable, as well as tough as old boots! If you cast someone who is too much of a little girl, she'll get lost in Oz.

"Dorothy is competing in Oz with an awful lot of scenery, as well as men in lion, tin and scarecrow suits. You have to be quite a performer to compete with that!"

These musical-theatre talent searches have proved an immense hit with viewers. Graham reckons they have resonated with audiences because they have an educative value.

"They sit very well on the 91Èȱ¬," muses the presenter, who has won three BAFTA Awards. "They could be dry and self-improving, but they're not. I've learnt so much from these shows – I was in La Cage Aux Folles because of them. And the viewers learn so much from them, too. As the series goes on, the challenges involve all sorts of skills vital for a West End performer."

One of the other attractions of these shows is the priceless rapport that has developed between Graham and Andrew. Over the past four years, they have become close friends.

"I love Andrew," Graham declares. "What I love about him most is that he's such a relentless enthusiast. He retains such a passion for what he does. Also, he and I tend to have similar opinions about the contestants."

Over The Rainbow, which is produced by talkbackThames, is introducing an entirely new judging panel, and Graham has been relishing the experience of collaborating with them.

"They're great," he beams. "It's been fantastic watching all three of them work with the girls. They all know exactly the right thing to say to get the best out of them."

Graham is convinced that viewers will connect with the contestants on Over The Rainbow, just as they did on How Do You Solve A Problem Like Maria?, Any Dream Will Do and I'd Do Anything.

"I think the nation will fall in love with the winner – that's why she'll win. People adore these shows because they're a celebration of excellence. Over The Rainbow is about people who are very, very good at what they do. From Andrew down, it is filled with amazing people, and viewers like nothing better than watching them."