HE'S the most successful, influential and powerful theatrical producer in the world and he's currently casting a spell over Southampton with his most magical of musicals.

Sir Cameron Mackintosh's Mary Poppins is enjoying a box-office busting four week run at Mayflower Theatre.

"It's a big old place and the show feels so theatrical here.

"It feels like a theatre that is loved and cared for and I'm thrilled with the business we're doing here. I can't remember the last time there was standing room only at so many performances.

"You get great audiences and it's a great place to play."

Bringing the tale of the world's favourite nanny to the stage was a labour of love which lasted several decades for the theatre impresario who has been producing more hit musicals than anyone else for nearly 50 years.

"I first tried to get the rights from Pamela Travers back in 1977 or 1978," he reminisces. "At that point, I just got a note back from her saying thanks, but no thanks. I know a number of people had tried and Jules Fisher who was having a lot of success with Beatlemania at the time had the rights, but the show never materialised.

"It wasn't a particularly original idea, but I felt we could do something special with it. I first read all the books the year I left school in 1964, the film came out in December 1964. They seemed to have their own language and syntax and they really stuck with me."

In a long-running saga mirroring the Disney battle to secure the rights for a movie, and the Tom Hanks film Saving Mr Banks based on the saga, it wasn't until 1993 when Cameron, by then working on the three longest running musicals of all time Les Miserables, The Phantom of the Opera and Cats, was to meet the writer of the Mary Poppins novels.

"She was 93 by that time and living in her little house off the Kings Road which looked just like Cherry Tree Lane. She was fragile but as sharp as anything."

The talks continued with Pamela Travers finally agreeing to drop her insistence on a completely new score rather than any of the songs popularised by the much-loved Disney film and Cameron Mackintosh started negotiations with Disney.

"She lived another three years after that, not long enough to see it unfortunately. Even though it was like a Mexican stand off to begin with, she became very supportive of the show. I hope she would have liked it. I think she was a bigger fan of the film than she let on!

"I finished writing it in the shadow of the Opera House in Sydney not far away from the theatre where she had become an actress. I felt that was right really."

The show first took to the West End stage in 2004 and has gone on to become an international hit.

The new version currently touring the UK is wowing audiences with its wonderful additional scenes, storybook set, all-dancing choreography and new songs, which seem to blend superbly with the originals.

"Dance just comes so naturally from her books, there's dance all the way through really, which is why I wanted (celebrated choreographer Sir) Matthew Bourne involved.

"I've known Julian (Fellowes, the script writer, best known for Downton Abbey and Gosford Park) for years since he was an actor and we worked with George (Stiles) and Anthony (Drewe, the songwriting duo responsible for music and lyrics on the show).

"Practically perfect (one of the new numbers) was practically perfect. It has not changed by one note or one word since the first day. The Sherman Brothers (the songwriting duo behind the movie's score) said they wish they'd written it!

"Neleus finding his father has really added to it and it's a huge production. Bob (Crowley)'s design has turned it into a far magical experience than even the original. All of us believe that this is the best version that's ever been done."

Poppins is not the only visit to the South Coast for shows by the prolific producer. Half A Sixpence, his musical adaptation of HG Wells's disguised biographical novel based on the author's unhappy apprenticeship as a draper in Southsea, opens at Chichester Festival Theatre next month. It's another hotly anticipated show from the creative team behind Mary Poppins.

Although yet to be officially announced, his multi-award winning musical Miss Saigon is expected to include Mayflower Theatre in its major UK tour in the summer of 2017.

But that's just a small part of the current work of the producer who has turned the West End musical into a global franchise.

Even by his own standards, he's currently pretty busy.

Cameron now owns eight historic London theatres, which he is restoring to their former glory, and is working on film versions of Oliver and Miss Saigon, to follow the huge success of the Oscar, Golden Globe and BAFTA award-winning Les Miserables, filmed partly in Winchester.

New shows are opening around the world and he itemises the whirlwind of activity around the time I meet him with obvious relish.

"On Monday, Les Mis is opening in Singapore, then Cats is opening in New York. We've got 40 different productions around the world. I'm lucky to have an incredible team of people working with me."

Known for his microscopic attention to detail, Cameron cites Cabaret and West Side Story as the shows he wished he'd worked on and can't quite choose a favourite from all of his 'babies'.

"I've got a whole orphanage," he laughs. "And I love working with them all. I suppose of all the shows I've done the most with Les Mis and that has much to do with Victor Hugo and one of the greatest novels ever written. I also really enjoy going back and making something better. I'm always thrilled to have that opportunity."

He may be a billionaire who has turned the notoriously risky theatre business into an empire, but he's happiest at home.

The 69-year-old lives in a stunning 13th century priory in Somerset which he and long-term partner theatre photographer Michael Le Poer Trench run as a thriving farm.

"I've got so many shows on which I need to go and see, so otherwise I only go to the theatre if I really want a night out or something really attracts me.

"On the whole I'm thinking where can I eat tonight or, more importantly, can I stay in tonight."

Mary Poppins closes tomorrow. Very limited tickets remain for today and tomorrow. Call 023 8071 1811 or visit mayflower.org.uk