The most popular item of old-fashioned snail mail in the doocots of arts journalists this week was a tiny envelope bearing a 1st class Large stamp (presumably to cover the weight), in which was what looked at first sight like one of those tiny tasting bars of Green & Black's.

In fact, the fake confectionary slid apart to reveal the plug for a USB socket on a computer, and the disguised memory stick contained production information and interviews with members of the creative team behind the new stage musical adaptation of Roald Dahl's Charlie And The Chocolate Factory. It previews at the Theatre Royal in Drury Lane, London, from May 17, but the press are not admitted until June 25, which signals not just that the producers are determined to get it right before showing it to the critics, but also that they are confidently settling in for a long run. There is no such thing as a sure-fire hit on the West End, but there is certainly an expectation that this show will run and run, and add to the already lucrative contribution that musical theatre makes to the UK's economy.

Bound up in that are two crucial components from Scotland. The adaptation for the stage has been written by David Greig, our most acclaimed contemporary playwright, whose recent international hits – somewhat smaller productions – are the National Theatre of Scotland's The Strange Undoing Of Prudencia Hart and the Traverse's Midsummer. To say that the author's daughter Ophelia Dahl, who chairs the literary estate, is happy with what Greig has done would be to understate her enthusiasm. "There's no question that David Greig has nailed it completely," she says. "He's managed to pull out some of the best bits and give it a completely new and fresh quality. You're going to be seeing things in the theatre that you've never seen before and haven't imagined. That takes great talent."

Some of that stage magic is in the hands of Jamie Harrison, who delights in the title of Puppet and Illusion Designer, and is better known round these parts as co-artistic director of Glasgow-based theatre company Vox Motus. That young company's inimitable visual style was most recently seen in a revival of Slick that toured across Scotland, and Harrison has had the considerable challenge of bringing the Oompa Loompas to the stage, an aspect of the new production that is shrouded in secrecy.

It seems obvious that, if all goes according to plan, Roald Dahl's Charlie And The Chocolate Factory, The New Musical, to give it its full publicity name, will be exactly the sort of thing that Maria Miller, the Culture Secretary at Westminster, was lauding when she spoke at the British Museum on Wednesday about the necessity for the arts to make a contribution to the economy. Her less than stout defence of the budget of her own department, in the run-up to the Government's annual spending review, was that only work that can actually generate hard cash is worthy of public subsidy. "When times are tough and money is tight, our focus must be on culture's economic impact," she said. "To maintain the argument for continued public funding, we must demonstrate the healthy dividends that our investment continues to pay."

Charlie And The Chocalte Factory is directed by Sam Mendes, whose recent work has included the most financially successful Bond film ever. But the Mendes career was built in the subsidised sector, specifically the Royal Shakespeare Company and the Donmar Warehouse. Jamie Harrison's work has thrived on the support Vox Motus has had from the Scottish Arts Council (SAC) and Creative Scotland. Greig came to the fore via SAC-supported Visible Fictions and then commissions from the Traverse and Tron theatres, and has been a very eloquent participant in the debate about the shape and necessity for arts funding in Scotland.

The commercial success in any sector of the arts in the UK would be starved of talent if it was not for the nurturing that is done with the benefit of subsidy – but that truth does not suit Maria Miller's argument.