Mr Hyman is thought to have been paid more than pounds 350,000 a year and is likely to receive at least a year's severance pay.
His departure after less than two years in the job is believed to have been prompted by Mr Hepher's decision to hire a new senior corporate finance specialist to bring together the businesses of Charterhouse and its two parent banks, CCF of France and BHF-Bank of Germany.
Mr Hyman's speciality is UK corporate finance and the new multinational structure left him out on a limb, leading to the decision to quit. Charterhouse said his contract was being terminated by mutual agreement.
The bank added that it was "looking to recruit a senior individual with a strong background of cross-border expertise and multi-cultural knowledge."
The bank and Mr Hyman said they had concluded that this new structure would not provide adequate scope for his creative talents and energy. The upheaval comes only three months after Mr Hepher arrived.