Crooks dressed in fake uniforms are turning up on the doorsteps of wealthy C Hoare & Co clients and duping them into handing over financial data that can be used to empty their accounts.
Britain's oldest private bank, founded in 1672, has written to customers about the scam which is targeting about three of its 10,000 customers a week and has seen one client scammed out of £500,000.
The crooks' operation begins with a series of e-mails from a fake Web site, often warning that the victim's computer has a virus, according to the Daily Telegraph.
This is then followed up with a personal visit from someone pretending to be a C Hoare & Co employee and wearing what appears to be the bank's distinctive uniform, complete with extensive braiding.
The fake banker then attempts to obtain the victim's Visa card or information which can be used to gain access to accounts and steal money.
Managing partner Alexander Hoare told the Daily Mail that the bank is trying to protect customers by urging them to "use our internet banking system, which is safer than post, or the mobile app once it is built'.