Hang Seng Bank yesterday announced Vincent Cheng Hoi-chuen would step in as a temporary replacement for former vice-chairman and chief executive Alexander Au Siu-kee who resigned last week. The temporary nature of the appointment surprised analysts, leading them to conclude Mr Au's resignation must have taken both Hang Seng Bank and its parent Hongkong Bank completely by surprise. Both banks have sought to play down persistent rumours there was a personal reason underlying Mr Au's decision to join rival Standard Chartered Bank, but the short-term nature of Mr Cheng's appointment has rekindled the speculation. Mr Cheng - who remains an executive director at Hongkong Bank - was unable to reveal how long he would stay at Hang Seng Bank, saying his appointment was the best available solution at the time. He added the group would need more time to consider making a permanent appointment, but again refused to give a deadline as to when that appointment would be made. Indosuez WI Carr analyst Anthony Lok said the fact Hang Seng's existing deputy chief executive Roger Luk Koon-hoo - one of the more likely candidates to replace Mr Au - was not appointed to the position in even an acting capacity indicated the job would not ultimately be filled by a Hang Seng staff member. Mr Cheng is the second senior executive to be sent from Hongkong Bank to Hang Seng after chief executive David Eldon who was appointed Hang Seng's chairman late last year. Others suspected Hongkong Bank might need time to assess Mr Cheng's ability, as he is a trained economist with no hands-on experience running the day-to-day operations of a retail bank. Mr Cheng yesterday admitted he was not familiar with every detail of Hang Seng Bank's operations but emphasised that he had good colleagues at the bank and did not think this would present a problem. He pointed out he had been managing director of Hang Seng since 1994 and had attended all its board meetings, occasionally participating in the bank's executive committees. Mr Cheng said he would propose no significant changes to Hang Seng's existing strategy as the 63-year old bank had been operating well. 'Given the current difficult economic environment this year is certainly not a year of aggression for Hang Seng and we would continue to put prudent management as our first priority,' he said. Mr Cheng said Hongkong Bank and Hang Seng would continue to be supportive of - and competitive with - each other. He declined to say if his appointment indicated further integration between the two banks, but said cost-cutting proposals would be considered if they were in the best interest of all the shareholders. Mr Luk said Hang Seng Bank had not cut any staff numbers but had redeployed personnel from one department to another as part of the bank's continuing measures to enhance efficiency. Mr Cheng joined Hongkong bank in 1978 and worked in the group finance department. He was in the group planning department between 1982 and 1985 before being appointed chief economist in 1986. He was seconded to the Hong Kong Government between 1989 and 1991 to work on the Central Policy Unit and was made senior manager of economic and strategic research in 1992. He was made chief financial officer in November 1994.