UPDATE 12:45 PM: Adds comments from Cirque du Soleil theater chief Scott Zeiger and more, below.

EARLIER: It’s more like a separation agreement than an all-out divorce, but Wednesday’s surprise management shakeup at London-based Ambassador Theatre Group is sending shockwaves through Broadway. Howard Panter and Rosemary Squire — the husband-and-wife team who founded what has evolved into the world’s largest live-theater-owning company — announced they are stepping off the ATG pyramid they’ve topped for 25 years.

Rosemary Squire & Howard PanterThey’re remaining on the ATG board and taking a chunk of the company — off-Broadway style producer Trafalgar Studios — as their own new fiefdom. Panter (the creative one) and Squire (the finance one) are being replaced by a business executive with no connection to the world of live entertainment except possibly opening-night parties: Mark Cornell, a former executive of Champagne producers Moët Hennessy and Krug and a former managing director of auction house Sotheby’s. He’ll now take the reins of a company with 45 UK theaters and 3,500 employees.

Most immediately significant on this side of the pond is the timing of the change for Broadway. ATG recently acquired two Times Square houses: one of the largest, the oft-renamed Lyric, with abut 1,900 seats, and the long-defunct Hudson, used in recent years as a corporate event space and now being restored by ATG as an intimate playhouse. The Lyric is currently home to Paramour, Cirque du Soleil’s first made-for-Broadway sit-down show, in previews and slated for a May 25 opening. Previews have been selling well, with grosses before deductions of around $1 million per week.

“I hope and believe the company will still manage and lead and grow the business with the same leadership and conviction as Rosemary and Howard,” Scott Zeiger, president and managing director of Cirque du Soleil Theatrical, told Deadline. “I’ve known Rosemary and Howard for 30 years and they had a lot to do with our getting the Lyric for Paramour. We’ve been told we will continue to interface with them.”

Panter and Squire have long been a welcome and much-admired presence, as much on Broadway as in the West End. “We are looking forward to devoting more time to our passion for creating great theatrical content and a vibrant London theater,” Panter and Squire said in a joint statement. “It is a good time for us to start new creative roles. We have thought long and hard before taking this decision but feel it is a time in our lives for an exciting new challenge.”

Like Cirque, the Montreal-based troupe that became a global sensation and was taken over last year by American-Chinese-Canadian financial conglomerate TPG, Ambassador has gone from the Panter/Squire mom-and-pop operation to a company whose reach includes ownership of Sonia Friedman Productions and other producing channels and recently was taken over by private-equity firm Providence Equity Partners, based in Rhode Island. With such turnover comes increased pressure for profitability.

In the ATG statement, Cornell said that ATG shows “significant potential for future growth” under his leadership, adding, “I am excited by the prospect of helping to shape and lead the next chapter in the life of this remarkable company.”

But like all change, the announcement brought out skepticism about the new owners, who will be the first Broadway theater owners who have no direct theater experience or tradition.

“Appointing a CEO with no known interest in the theater, and the reality of the bottom line of ATG as it stands, leaves very little room for doubt as to their path,” a prominent independent producer told Deadline, speaking anonymously to protect possible future collaborations. “In the end it is very fortunate for for both London and New York that the rest of the theaters will never fall into the hands of money men. I am very fond of Howard and Rosemary but from day one doing business with these types mean only one thing.”

Countered Zeiger, who has seen several companies he’s worked for transition from from one kind of business culture to another: “I’m no stranger to private equity,” he said. “TPG has been incredibly supportive of my crazy, wild show at the Lyric. Nothing leads me to believe that will change.”