Even his snootiest, most cynical critics acknowledge that, for every new Mackintosh mega-musical clogging up a West End theatre, there is a delightful flip-side in the spectacle of a relatively poverty-stricken director previously committed to the subsidised theatre made rich beyond his (so far they have all been male) wildest dreams. Just as he knew Miss Saigon needed Nick Hytner’s unsentimental, astringent treatment, so he believes that Martin Guerre will be best delivered by Cheek by Jowl’s director-designer duo, Declan Donellan and Nick Ormerod. “Having seen their Fuente Ovejuna and Peer Gynt, I felt that peasants is what they’re good at.”Fairy-godmothers don’t come sweeter than Mackintosh. Little by little he is masterminding a redistribution of theatrical wealth. “I’m convinced that, with most story shows, authors should create first. The director and choreographer shouldn’t be brought in before there’s something to root out.” Nor does he continually recycle the same tried and tested talents. Unlike most impresarios, he doesn’t merely assemble a team, then find the money for them to create the show.

He knows what he likes and his wishes become commands very early on. “You can only care about what happens to characters if you like them.” He didn’t want any flashbacks, “which I don’t believe belong in a musical”. Some previewers have called it a Les Mis rehash (not surprising, given the Schonberg/Boublil factor, and not necessarily a criticism), others emerged a little hazy about what had actually happened, claiming it wasn’t the story – basically, mystery man returns from war to reclaim wife and property – they thought they knew from the Gerard Depardieu film.Mackintosh says he wasn’t wild about the movie: he disliked “the selfish, calculating character” Depardieu played. He starts gushing about the “naturalistic sound – I don’t think anyone will know it’s amplified” and the wonderful set, five structures swivelling like a vertical kaleidoscope, and the trees – “copies of real trees from Epping Forest”.

It may be a show about peasants, but Mackintosh’s idea of rustic doesn’t mean hick. A new lyricist, Edward Hardy, a graduate of Sondheim’s masterclasses, took over from Herbie Kretzmer and, according to Mackintosh, has given the show the “sophisticated but rough-hewn quality” he says it needed.”I’m terribly pleased with how it’s going,” he admits, suddenly consumed with a snuffling, rather embarrassed and childlike excitement. First, Boublil and Schonberg were late with the product and Declan Donellan, the director, was left to occupy his cast with potato-picking workshops; then, even after previews began a couple of weeks ago, Mackintosh still spent the days “fiddling round, working on the clarity, the pacing”. I realised that everything was there and it was just a matter of threading it all together.”It’s still taken some doing.

We sat down at 11 o’clock and by the end we’d discovered the integral part of the show. Even stars weren’t really necessary any more, the show itself hogged the limelight. Last year, musicals made up 62 per cent of all West End theatre attendances, while new drama drew 11 per cent, revivals only eight. Of 19 musicals now running, the five with the queues furthest round the block are Mackintosh’s.Will Martin Guerre bring him the same success? Claude-Michel Schonberg and Alain Boublil – who are reputedly coining pounds 20,000 a week for their contribution to Les Mis – first came to him with the idea six years ago He didn’t like it.

“It didn’t have the sweep that is their trademark.” He heard it again in 1993 and didn’t like it any better: “There were terrific nuggets of Boublil and Schonberg songs in it but it hadn’t come together.” He sat down and explained why he wouldn’t be getting involved “It was one of those extraordinary days. This innovatory show, staged by people who apparently cared about its literary roots as much as its physical spectacle, set the tone for the future. Arguably, from this point on, the British theatre became internationally famous not for the quality of its new writing but for its outstanding ability to stage spectacular musicals. Maybe it’s the way he dishes it out, but nobody seems to resent him for it. Indeed, it appears that they trust his judgement (“I call it instinct”) better than their own, which is hardly surprising given his hit rate. At the last count, Cats had turned over pounds 1 billion, Les Mis pounds 750 million, Phantom pounds 1.4bn, Miss Saigon pounds 500m.