The decision was taken by the firm’s board, which agreed unanimously that Letley become the new CEO.
Letley took over as interim CEO from Jason Britton in July after Britton became CIO with the retirement of Richard Martin from the role.
Letley has held similar high-profile roles in other financial organisations including the HSBC Group.
T. Bailey is also planning new sales appointments shortly.
T. Bailey chairman Nicholas Forman Hardy says: “Peter brings a huge amount of experience in running a financial business and with that comes enormous clarity and vision to decision making.
“He is a real asset and I am thrilled he has joined us on a permanent basis.”