Aon has acquired the commercial insurance broking business of Royal Bank of Scotland and NatWest for an undisclosed sum.
The deal means Aon will now sell commercial property and liability cover to the bank's existing corporate clients under its own brand name. Around 20 in-house staff now join the Aon payroll from the bank's Glasgow office.
A spokesman for the Royal Bank of Scotland said the bank had decided to sell its commercial arm because the business was not "significant" and did not fit into the group's long-term strategy.
"This is such a specialist area, we felt a company like Aon would better serve our customers.
"We have been restructuring our insurance division and focusing on the pet, home and general personal lines sector," he said.
He added the transition had been smooth and the bank's existing clients had not suffered from the takeover.