Knott was GIB's chief risk officer helping the bank in the process of becoming regulated by the Financial Conduct Authority (FCA), the UK's financial market watchdog.
He takes up a new role in the bank as finance director Jeremy Burke moves to a role in the strategy team, the bank said.
GIB Chairman, Lord Smith of Kelvin, said: "Now we have moved beyond the start-up phase it is important that we build the infrastructure we need to support our long-term future as an enduring institution."
The bank also announced the appointment of Laurence Mulliez as a new non-executive director. She will sit on the banks investment committee.
Mulliez has 20 years commercial experience commercial experience. Most recently she was chief executive at Eoxis Renewable Energy, an independent renewable energy provider.
Last year, the bank announced plans to raise £1 billion (EUR 1.25 billion) to acquire stakes in operational offshore projects.