IT is one of the most eagerly anticipated new musicals in London's West End, a lavish staging of one of the world's best-loved children's books.

But Charlie and the Chocolate Factory will also mark a significant step into the musical spotlight for an acclaimed Scottish playwright.

David Greig, the award-winning writer of plays such as The Strange Undoing Of Prudencia Hart, Dunsinane and Midsummer, has written the script for Roald Dahl's Charlie and the Chocolate Factory, which will open at the London Palladium in June next year, directed by the Oscar-winning movie and theatre director Sam Mendes.

Greig has worked for three years on what is called the "book" of the musical, which will feature new songs and a new take on Dahl's famous story, which has already been made into two movies: Willy Wonka & the Chocolate Factory in 1971 and Charlie and the Chocolate Factory in 2005.

Yesterday, Greig, who was born in Edinburgh in 1969, said that despite the size, scale and budget of the Palladium endeavour – which is likely to generate a significant payday for the writer – producing the book has been much the same as writing any of his other plays, although he admitted there is "significant baggage" around the story.

"It is odd because I have not really experienced that much difference in what I do," he said.

"Obviously it is different when I write a simple line – 'Charlie enters the Chocolate Factory' –and then I see the incredible beauty and incredible opulence of what they are going to do on stage, that is something else.

"But at a fundamental level what I am doing is the same as before as when I wrote 'Prudencia Hart escapes hell' for a piece of carpet with a table and two actors [for the National Theatre of Scotland].

"Undoubtedly there are pressures, but with a major production for the West End theatre, the writer of the book for a musical is really quite a long way down the chain.

"I really, really believe that if you tell the story well, everything else will fit, and that releases everyone else to do their jobs."

The musical, which will open after a preview period, is being staged by Theatre Ventures, the play and musical division of Warner Bros, with tickets going on sale in October.

Greig said he has not been influenced by the two movie versions of the story, which was first published as Charlie and the Chocolate Factory in the UK in 1967.

"We watched the films, indeed Warner Bros owns the rights to them. The first film [starring Gene Wilder as Wonka] is the holiday film in the US, it is shown every Christmas, it's an institution and people can quote from it at length," he said.

"The thing is with this book is that everyone feels ownership of the book. Everyone wants to be Charlie, everyone wants to have the Golden Ticket, everyone wants to see the factory – so yes, there are some significant boots to fill and baggage to carry.

"But we were determined, very early on, to create our own version and tell our own story, and Sam has been very supportive all the way through."

Greig, who recently spoke out about his concerns for the future of the arts in Scotland following controversial funding changes at Creative Scotland, said the musical was not yet "finished".

He said it was evolving all the time, with contributions from himself, Mendes, and song- writers Marc Shaiman and Scott Wittman changing the piece as it moves closer to being staged.

"It has been brilliant fun, and excellent experience, but it is not yet finished – the process of making a musical on this scale is a huge undertaking and it has very many phases."

He added: "There is huge involvement from design, there are rehearsals and previews, there is a constant process of change.

"So we are still in that process. As far as my own experience as a writer - so, far the only real difference is that when I go to London I stay in slightly nicer hotels."

Warner Bros is currently making other movies into musicals, including Misery, Beetlejuice, Dave and Secondhand Lions as well as Andrew Lloyd Webber's version of The Wizard of Oz.