London ? Cameron Mackintosh will bid “adieu” today to his Broadway production of “Les Miserables,” but the British producer says the imminent departure of a musical fondly known as “The Glums” has not got him down.

“I feel complete happiness,” said Mackintosh, 56, about a musical with a heavy story line that ends in death. He was speaking a month before he rings down the curtain on the epic show adapted from Victor Hugo’s novel.

“This is a piece where I can absolutely, categorically and without any bias say that there is no reason why ‘Les Miz’ will not be performed regularly for as long as anyone goes to see a musical.

“That plot and that score will never date; it’s a completely timeless animal.”

Not to mention an incredibly lucrative one. In the 16 years since “Les Miz” opened in March 1987 at the Broadway Theater, transferring in 1990 to its current home at the Imperial, the New York production has grossed more than $400 million. (That figure includes its two-month pre-Broadway tryout at the Kennedy Center in Washington, D.C.)

It paid back its $4.5 million production costs in 33 weeks between Washington and New York, where the top ticket price has more than doubled — from $47.50 in 1987 to $100 today.

Mackintosh has presided over four of the most successful international musicals of all time, starting with composer Andrew Lloyd Webber’s “Cats” and on to “Les Miz,” “The Phantom of the Opera” and “Miss Saigon.” But with only “Phantom” still enjoying an open-ended Broadway run, the producer said the decision to close “Les Miz” was a matter of timing.

“You’ve got to know at the point when you take something off that it can still go off with all colors flying,” Mackintosh said in an interview from his country estate south of London. “Like anything in life, it’s a sense of judgment.”

Weathering tough times

But he said the lingering impact of Sept. 11 had played its part. “Les Miserables” and other Broadway shows suffered sizable drops in business following the terrorist attacks. Shows shut down for three performances, costing producers an estimated $3 million in lost revenue. And with tourism down, business was slow to return.

“Shows carry very small advances compared to what we have got used to for 15 years,” Mackintosh said. Even the current revival of “Gypsy,” starring Bernadette Peters, opened May 1 to an advance ticket sale of $5.75 million as against the $12 million advance that once greeted “Les Miz.”

“Les Miz” had posted an earlier closing notice of March 15 to coincide with its 16th birthday, but strong last-minute business kept it going a while longer.

Producer Cameron Mackintosh, second from right, thanks the audience, as the cast of Les

Why not into the summer? Because, says Mackintosh, that is the time generally given over to the shows that clean up at the Tony Awards, and the Tonys, the producer points out, “are all about new shows, quite rightly.”

“Les Miz” won eight Tonys in 1987 and fueled Mackintosh’s subsequent box-office bonanza, “Miss Saigon,” with composer Claude-Michel Schonberg and lyricist Alain Boublil. “Phantom” hit Broadway early in 1988.

“There will come a point where Andrew (composer Andrew Lloyd Webber) and I will go, ‘Now, it is Phantom’s turn to come to the end of it first life,”‘ Mackintosh said. But no closing date has been announced.

Successful revivals

The 1990s weren’t as kind to the new musicals from the Mackintosh stable, with “Martin Guerre” — another Boublil-Schonberg collaboration — and “The Witches of Eastwick” underperforming compared to the previous decade’s spate of hits.

In recent years, the producer has had greater success with revivals (“My Fair Lady” in London, for example), even if last season’s much-anticipated new Broadway production of “Oklahoma!” only paid back 60 percent of its costs.

New musicals are tougher, Mackintosh acknowledges, not to mention a young man’s game. “That’s one of the reasons I have decided I don’t want to be there on my white charger; I’d much rather be here, gazing into my garden.”

But he is not getting out the business. Far from it: Mackintosh is preparing a musical version of “Mary Poppins,” in collaboration with Disney, to open on the West End late in 2004.

Academy Award-winner Julian Fellowes (“Gosford Park”) is adapting the P.L. Travers stories for the stage, with new songs from George Stiles and Anthony Drewe to buttress the existing Sherman brothers score from the 1964 film.

“The thing we have to deliver is something very special to live up to and beside the fantastic movie,” says Mackintosh. Richard Eyre, one-time director of Britain’s Royal National Theatre, is scheduled to direct.

“There is no way I am not going to continue as a producer,” says Mackintosh. “After 35 years, I’ve built up a fantastic amount of material … shows that are going to be produced long after I am dead and gone.”