RSA Insurance Group Plc said the head of its U.K. and western Europe business will leave the company, marking the second resignation of a senior manager since Stephen Hester was hired to revamp the British insurer.

Adrian Brown, a 25-year RSA veteran who ran the U.K. business since 2008, is departing to become executive chairman of underwriting and distribution at Arthur J. Gallagher & Co., London-based RSA said in a statement today. He has resigned from RSA’s board and will leave his executive role once his successor is named.

“We will miss him when he leaves but look forward to a strong relationship continuing at his new employer,” Hester, RSA’s chief executive officer, said in the statement. “It provides the opportunity to appoint new leadership in this key part of our business. We have an ambitious business plan which now needs to be driven over a time horizon that Adrian could not reasonably commit to.”

Hester, the former CEO of Royal Bank of Scotland Group Plc, was drafted in to turn around the U.K. insurer this year in the wake of an accounting scandal at its Irish unit. Yesterday, he named the CEO of emerging markets, Paul Whittaker, as group chief operating officer.

RSA’s CEO of Scandinavia Mike Holliday-Williams is due to leave the insurer next month to join Direct Line Group Plc.