However, Peh said building ties with mainland authorities was not his first priority.

On his first day of work last Monday, the 56-year-old said his relationship with Chief Executive Leung Chun-ying, who appointed him to head the 38-year-old anti-graft watchdog, was strictly professional.

'Mr [Donald] Tsang [Yam-kuen] is my former boss and Mr Leung is my current boss,' Peh said. 'Our relationship is a boss-and-subordinate relationship. We do not have any private friendship.'

But Peh admitted that he had met Leung and various ministers-designate before his official appointment 'to get acquainted' with them, which raised questions about the commission's independence.

While Peh is legally obligated to report to Leung, his admission on his relationship with the chief executive nonetheless drew criticism from former ICAC investigator Stephen Char Shik-ngor.

'The ICAC is an independent institution,' Char said. 'It is not the chief executive's private weapon. It needs to be accountable to all Hongkongers. Hongkongers are the bosses of the ICAC, not the chief executive. He [Peh] needs to have such an understanding,' Char said, adding that he had not heard such admissions from previous ICAC chiefs in his 28-year career at the commission.

Char, now a barrister, worries that Peh's description of his relations with Leung would diminish the commission and affect the independence of its probes of such officials.

In his new role, Peh may find himself having to investigate both Leung and Tsang. Leung is facing legal challenges and calls for his resignation for making false election claims that he had no illegal structures at his home on The Peak. Six such structures have since been uncovered.

As for the former chief executive, Tsang came under fire for dealings with his tycoon friends, such as accepting rides in their private jets and yachts and agreeing to rent a luxury penthouse in Shenzhen at a bargain rate. The ICAC's biggest case now is its probe of former chief secretary Rafael Hui Si-yan and the tycoon siblings of Sun Hung Kai Properties - Thomas Kwok Ping-kwong, Raymond Kwok Ping-luen and Walter Kwok Ping-sheung. The commission is still consulting with the Department of Justice on whether to file charges against them.

All these incidents and cases are now widely seen as Peh's top priorities as the ICAC's commissioner.

Peh has pledged to fight graft without fear or favour and to educate the public to prevent graft. He also views his 33 years of immigration service as an advantage in helping him tackle challenges at the ICAC.

However, former ICAC investigator Char disagrees that Peh's experience would be useful in his current role, given that the commissioner would not be directly involved in investigation work. Daniel Li Ming-chak, the ICAC's head of operations, is more experienced in probing graft cases than Peh, Char says.

Prior to Hong Kong's handover in 1997, high-calibre, former government ministers were often appointed as ICAC commissioners as their last civil service role. That was because they could investigate their former colleagues with few fears of reprisals, according to Char.

Char argues that Peh's appointment has tarnished the position of ICAC chief, but he is not the first former immigration chief to lead the ICAC.

In July 2002, former immigration director Ambrose Lee Siu-kwong was appointed as head of the ICAC. A year later, he succeeded Regina Ip Lau Suk-yee as security secretary.

Lawmaker James To Kun-sun also questions Peh's commitment to social values.

'With a mindset of disciplinary force, he [Peh] would overlook many other social values such as human rights,' said the Democrat and chairman of the Legislative Council's security panel.

But a former immigration officer who had worked with Peh says he would be good in his new role.

Describing Peh as kind, discreet and gentle, the officer, who declined to be identified, says Peh's experience in law enforcement will be an asset because he will take greater note of operational considerations in making decisions.

Furthermore, Peh's experience in handling politically-sensitive issues when he was director of immigration would stand him in good stead, the officer said.

Peh joined the immigration department in 1978 and had worked his way up to become the director in 2008. He stepped down last year.

As an assistant director in 2003, Peh helped enact the Capital Investment Entrant Scheme, which has attracted more than HK$106 billion in investments to the city to date.

During his tenure as the director of immigration, Peh's biggest mistake was a 'slip of the tongue' warning of possible terrorist attacks at the 2008 Olympic equestrian events in Hong Kong, which drew global attention.

Besides the prospect of probing the city's rich and powerful, Peh is facing an exodus of experienced investigators who are retiring soon.

Of the 27 principal investigators and assistant directors at the ICAC, 13 are in an acting capacity.

Peh told the South China Morning Post that he was well aware that a number of senior officers would soon be leaving after serving the ICAC for more than 30 years. They include Daniel Li, the operations chief, who oversees all the investigators. Li is retiring this month.

Peh stressed that the ICAC had a long-term succession plan in place and competent officers with potential had been groomed for the top positions.

In any case, Peh's first task is probably to secure the confidence of the public.

With his e-mail inbox filled with potentially politically explosive cases, Peh surely has his work cut out.

SIMON PEH YUN-LU

Age 56

Currently

Commissioner, Independent Commission Against Corruption

Previously

Director of Immigration, April 2008 to March 2011. Joined the government as immigration officer in April 1978

Education

A bachelor's degree in biochemistry at the Chinese University of Hong Kong and a master's degree in international relations at King's College, London

Personal

Married with one son