Jacques Aigrain arranged plenty of deals during his 20 years as an investment banker at J.P. Morgan, where he rose to become co-head of M&A in the late 1990s. But Aigrain's latest deal, in which he's the buyer rather than an adviser, is by far the most important to him.

The 51-year-old CEO-designate of Swiss Re helped negotiate the $6.8 billion purchase of GE Insurance Solutions, General Electric's reinsurance subsidiary, in November. The deal will give Swiss Re more than $6 billion a year in premium income and enable it to overtake Munich Re as the world's biggest reinsurer.

Aigrain won't gloat about that fact -- he is more interested in earnings growth than in market share. But lately, he allows, the two have become more closely linked. Huge losses related to Hurricanes Katrina and Rita in the U.S. this year underscored the importance of having a diversified business and a strong balance sheet, he explains.

Those prerequisites also make clear why few new players are entering the reinsurance business despite rising premium rates. That's a big change from the aftermath of the September 11, 2001, terrorist attacks. "Diversified, global multiline reinsurers like Swiss Re are in a position of strength, and monoline bucket shops are less reliable," Aigrain says.

Paris-born Aigrain, who joined Swiss Re as head of its financial services businesses in 2001, succeeds John Coomber as CEO in January. He credits his predecessor with turning the company around after terrorism-related losses and declining stock markets pushed Swiss Re deeply into the red in 2001 and 2002. "If it wasn't for John Coomber having worked so well at improving the capital strength of Swiss Re, this deal wouldn't have happened," Aigrain says.