The first two branches in Holborn and South Kensington will open in early June, with two more in Kensington High Street and Fulham Broadway to follow later in the year.
Founder Vernon Hill said he wanted to emulate the feel of higher-end retail outlets in a banking format. Each branch will be open from 8am to 8pm on weekdays with shorter hours over the weekend, including Sundays.
No glass screen will separate customers from tellers and, as revealed by City A.M., dogs will be welcome.
Hill said he planned to open 200 outlets in the Greater London area within a decade.
He added: “It’s not just about delivering a large branch group, it’s about delivering great service at each branch.”
Hill, who made $8.5bn (£5.6bn) in 2008 when he sold his Commerce Bank start-up, said the big banks had thrown away their advantage, adding: “We are about bringing a service-based customer model.”