The new appointment is expected to boost its private banking operations in the UK and return to profit, said the bank.
Prior to holding current position, Lewington worked as head of the absolute return fixed income team at Union Bancaire Privee in London, and earlier, as head of Active Global FI (ex-US) at State Street Global Advisors.
Brock joins JP Morgan from Bernstein Global Wealth Management, where he was acting as a client advisor covering the North East region of the US.
Walden served as head of private client banking activities within Investec Private Bank, and prior to that held number a of positions at Kleinwort Benson Investment Management.
JP Morgan’s head of UK private banking Olivier Givenchy said the appointments confirmed the private bank’s commitment to further growing its footprint in the UK.
The selection of new bankers is also part of the private bank’s strategy to launch a service dedicated to the high net worth community, in addition to its offering for ultra high net worth individuals.
JP Morgan’s net income in the first quarter of 2012 was $5.4bn, down from $5.6bn during the corresponding quarter of 2011.