Colin Jelley worked for Skandia for 18 years from 1993 to 2011, before his return earlier this year.
The company confirmed his departure in a brief statement.
It read: "Colin Jelley has left the business by mutual consent having helped build our team of wealth planning specialist to 10 people this year.
"That team will now report into Nigel Jeffries, head of strategic relationships, and will continue to offer financial advisers expert wealth planning support. We wish Colin well for the future."
He moved to St James's Place in 2011, working for two years as a private client director.
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Mr Jelley, a member of the UK technical committee in the Society of Trust and Estate Practitioners, said on his return to Skandia in February he was "excited about being part of its future as a wealth solutions business", also calling it an "ambitious" firm.
Steve Powell, UK sales director for Skandia, said when he returned that he was "delighted" to have him back because his
"vast wealth of knowledge and expertise is second to none".