Antoniades, who joined the firm in 2003, has left after six and a half years.
Previously, Antoniades worked as a mortgage adviser for St James’s Place from 1995 to 2003.
He says: “I have no immediate plans but I’m sure opportunities will come along. There maybe some PR opportunities but we’ll wait and see what happens.”
He adds: “Whatever move I make it is definitely going to be within financial services. I don’t need to rush into making any decisions because my next move has got to be also for a term of at least or not longer than what I did at Quantum.”