Bennett has nine years of experience in the fund management industry and his appointment follows Argonaut’s hire of Edward James as chief operating officer in August.
Argonaut was set up in 2005 by Barry Norris (also formerly at Neptune) and Oliver Russ, in a joint venture with Ingis Asset Management.
Norris looks after Argonaut’s three Alpha funds, while Russ manages the firm’s equity income funds.
Bennett, who will support both Norris and Russ as an investment manager, has worked on both equity income and opportunities funds in the past, but has previously focused on the US and UK.
Norris said: "Having worked with Greg for four years at Neptune, his qualities are well known to us. He will be an invaluable addition to the team."
In August Ignis confirmed that Argonaut was to become an operationally independent firm, with the partners upping their stake to 60% and taking management control.