Seventeen years ago a pair of theatre obsessives went into business together to build a theatre in Woking.

Yesterday Howard Panter and Rosemary Squire, as husband and wife, celebrated the £90 million acquisition that makes their company the largest British theatre operator since the variety era, dwarfing Lord Lloyd-Webber and Sir Cameron Mackintosh’s rival empires.

It is an extraordinary story and one that could have distinct consequences for theatregoers, particularly in the regions, where the Ambassador Theatre Group (ATG) now has five times as many seats as any other operator.

Supporters praised the couple for their dedication to the theatre, which has led ATG to become one of the most dynamic producing outfits in the country. Their output ranges from Glyndebourne to pantomime, from edgy fringe theatre to Keira Knightley’s imminent West End debut in The Misanthrope.

Sonia Friedman, the producer of the recent West End hits La Cage Aux Folles, That Face and No Man’s Land, whose company is a wholly owned subsidiary of ATG, described them as enthusiasts who were animated by “new work, new ideas and young writers and directors”.

“Both Howard and Rosemary started right from the bottom, with no money and no resources and worked their way up. They have got here by sheer tenacity, passion and incredible will.”

She said that the deal — in which ATG will take over the theatres of the concert organiser Live Nation — would lead to more quality productions touring the regions.

However, concerns were also voiced last night about the commercial clout that the expanded group will have.

David Pugh, the Tony award winner, producer of God of Carnage and a prolific organiser of regional tours, recalled how a generation ago Apollo Leisure Group owned a large portfolio of regional theatres and would dictate terms to touring companies. “They would insist that we visited loss-making venues and that they got 30 per cent of the box office — which is a terrible deal.

“I don’t think monopolies are ever a good thing and I would be saying the same if Cameron Mackintosh had bought them all.

“I like Howard and I think that ATG run their theatres well, but I am worried. Power corrupts,” he added.

ATG was the only British contender bidding for Live Nation’s theatres.

The successful acquisition values the new expanded company at £150 million and was made possible by investment from Exponent Private Equity, which has become ATG’s majority owner.

ATG’s private shareholders include Greg Dyke, the former Director-General of the BBC, and the property entrepreneurs Sir John and Peter Beckwith. Mr Dyke is the new executive chairman of the group.

In all, ATG now owns 39 theatres, stretching from Glasgow to Torquay. That will rise to 40 when the Aylesbury Waterside Theatre opens next year. Their theatres range from regional behemoths such as the Edinburgh Playhouse, the Liverpool Empire and the Bristol Hippodrome to the intimate Donmar Warehouse and Trafalgar Studios in Central London.

The giant scaling-up of the business is a bold move after a year when the company made a pre-tax loss of £603,000 to September 2008.

It is also a far cry from the company’s humble beginnings, setting up what is now the Ambassadors Woking complex in 1992 and, just after that, putting together a consortium to buy the Duke of York’s Theatre in the West End from Capital Radio.

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