Aon Plc Chief Executive Officer Greg Case, who moved the insurance broker to London from Chicago four years ago, said the U.K.’s centuries-long leadership in the industry would be damaged if voters choose to leave the European Union.

“The U.K. has been at the center of insurance and risk management since maritime trade and shipping was insured at Lloyd’s in the City of London more than 325 years ago,” Case said in a letter posted Monday on the company’s website. “Leaving the EU jeopardizes the U.K.’s leading position in the epicenter of our global service economy.”
Industry leaders have been stressing the benefits of global commerce, along with the risks of isolationism, ahead of the June 23 vote. American International Group Inc. CEO Peter Hancock said last week that he’d consider establishing a European operations hub beyond London if the “Leave” side prevails.

Case said Aon may not be able to provide the same coverage options to clients if trade barriers increase. He also said the company would find it harder to recruit and retain top talent.

Aon moved its headquarters to the U.K. in 2012, citing improved access to Lloyd’s of London and emerging economies. Lloyd’s is the world’s oldest insurance market and is used by businesses seeking to guard against large or complicated risks. Aon’s shift also provided tax benefits.

Managing Risk

Case’s company acts as a middleman in the insurance industry, helping clients arrange coverage to guard against risks ranging from natural disasters to bed bugs to lawsuits. It is the second-largest broker by market capitalization to New York-based Marsh & McLennan Cos.

“In our world, risk is inevitable and we manage it accordingly,” Case wrote. “But leaving the EU is an unnecessary gamble.”

Aon climbed 95 cents to $107.81 at 12:13 p.m. in New York, extending its gain for the year to 17 percent as global stocks rallied after weekend polls showed “Remain” prevailing in the U.K. vote. Marsh & McLennan rose 76 cents to $66.62 and is up 20 percent since Dec. 31.