Torquay broker Michael Pavey Westinsure has won the prestigious National Trust account from Marsh.
The account is understood to be one of the largest charity accounts in the country.
As part of the three-year deal Pavey will expand its Exeter office. It said it expected to increase the office's premium income by more than 30% to £13.5m.
Graham Brown, a Pavey director who previously serviced the account for Marsh, said the National Trust had chosen the small broker to run the book after Marsh cut staff from its Exeter office.
He revealed that Pavey had hired six ex-Marsh employees, three of whom will handle the National Trust account.
"The National Trust wanted continuity for the account and to maintain the relationship it had established with the [Marsh] team," he said.
Brown said the three other former Marsh staff would drive its development programme.
He added that Pavey plans to recruit more staff to develop its charity account and grow its commercial book.