Richard Wohanka, the largest single shareholder, will become non-executive chairman and Phil Smith will become chief executive.
Mr Wohanka was previously chief executive at Swiss private bank Union Banc Privee and has over 30 years of asset management experience. Mr Smith was previously managing director and global management committee member at Barclays Wealth and has particular background in business transformation. 
Tim O'Connor has been appointed as managing director of proposition and distribution and there will be a new appointment to the role of managing director of operations and process.
Current managing director David White will continue at the firm as a board member and senior executive.
The process will mean multiple small dormant shareholders will leave the ownership group and all executive shareholders will retain their full holdings.
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Mr Wohanka said: "I am extremely excited to be able to invest in this business. Hornbuckle Mitchell has the right critical mass, the right expertise and the right distribution partners to continue to win in the retirement market.
"We will augment what it already does well and invest in all of the facets which make a great business- client service, technology and process, product innovation and people."
Mr White said: "I am delighted to have successfully attracted our new investors to the business. They bring both capital and a depth of expertise which will be the envy of the independent Sipp market."
The transaction has been approved by the Financial Conduct Authority but is subject to closure conditions between the parties.

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