Mark Elwood, the head of art and design at Fallon, is understood to be in talks to join the new agency as a partner.
Elwood joined Fallon as head of art and design in 2004. Prior to that, he was head of design at Abbott Mead Vickers BBDO.
The name 101 is inspired by the date of the shop’s first day of trading, 10 January. The agency's offices will be based at 9 Rathbone Place.
The management line up also includes the founding partner Steve Waring, previously the chief financial officer at Saatchi Saatchi Fallon Group.
Plans to launch the start-up were revealed in September last year.
At the time, Green described the privately funded shop as operating as a collective of people working in a new way that can "take up the shape that tasks demand".