Hugh Mullan, whose career has included roles at Barclays, Schroders and Citibank, joins Multrees Investor Services as a non-executive director.
Previously, he was the UK chief executive at Fidelity Worldwide Investment.
His new company is an independent custody and consolidated reporting specialist for wealth managers and family offices.
He joined Fidelity in 2008 from Barclays Wealth where he held roles as chief operating officer of the Investment and Product Division and as global head of operations.
Nigel Pilkington, chairman of Multrees, said: "Attracting someone of Hugh's calibre to Multrees is incredibly exciting for the business. "He is exceptionally talented across a broad range of business needs, making him an ideal individual to help provide further industry expertise and guidance to the Multrees board."
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Whilst at Fidelity, Mr Mullan was a member of the company's Global Operating Committee and, prior to his UK CEO role, he managed customer services, operations, technology and fund accounting across all of Fidelity's European businesses.
He has also held senior business and operations roles at Schroders and Citibank.
Mr Mullan said: "I am delighted to be joining Multrees at this important stage in its development. These are interesting times for wealth managers as regulation and increasing customer sophistication challenge business models. Through its investment in modern technology, and its strong service focus, Multrees is well-positioned to support the growth and success of its clients."
Chris Fisher, chief executive of Multrees, said his experience of the investment, IT and wealth management industries, alongside his in-depth experiences across operations, makes him an "invaluable asset".