This enthusiasm is not confined to new recruits waiting to march into Police College at Wong Chuk Hang. More than 31 years after he joined the Royal Hong Kong Police, Mr Tang gets out of bed at 5am; he can't wait to get to work. While morale may be high, he is not taking things for granted. It's his job to ensure the present state of contentment and commitment stays at that level, he says.

Indeed, that applies to several aspects of his job. Corruption is down, but it's going to require constant vigilance to make sure it stays that way. Crime rates are satisfactory. Only hard work by police officers on the streets will keep it in check.

Hong Kong has never had a serious terrorist threat. Mr Tang, who spent more than six years in the secretive anti-terrorist squad, the Special Duties Unit, is determined that ceaseless training and planning to protect potential targets is going to frustrate any plot.

Surveys show 83 per cent of the public support the police. What about the other 17 per cent? Mr Tang asks. Why aren't they in favour?

Our reputation as one of the world's safest cities is something he is determined to maintain. Thankfully, he notes, Hongkongers by and large are law abiding and support their police force. On all these fronts, and many others, there is endless planning and training.

Take corruption. Reviews by the Independent Commission Against Corruption show nothing to suggest that there is any organised corruption in today's force. All figures indicate a continuing downward trend in officers being involved in graft, most of it minor.

'But there's no room for complacency,' Mr Tang said. 'We're very pleased to see it but we're still trying harder. We've got internal committees examining how to prevent corruption opportunities. We make staff very aware there is zero tolerance. We tell every officer it's his or her duty to fight corruption and to report any suspicions.

'We teach them how to avoid traps. We constantly review our practices. All senior officers must

be alert for opportunities for corruption, no matter how remote.'

There is now a very good relationship between police and the ICAC, a far cry from the virtual state of war between the two law enforcement agencies when Mr Tang graduated as a probationary inspector. The major challenge facing the force today is to keep Hong Kong's status as a safe and stable city.

'That's our promise,' he said. 'We're an international city, a trading hub, a travelling hub, a cosmopolitan society, a place where we hold major events including commercial trade fairs, sports and cultural festivals.

'We receive a million visitors a month from the mainland. There are a lot of challenges.'

One is terrorism. 'We are an international target,' said the man who was in charge of the airport and was a senior planner for the 1997 handover ceremonies, assignments where terrorism was a major consideration. 'I'm not suggesting we're in danger,' he said. 'But we're a potential target. We've got a sizeable international community. We've got all the ingredients.'

One tactic is to watch closely what happens overseas and to maintain excellent intelligent links with foreign counterparts. Another is to assess risks. Two years before the World Trade Organisation met here and unruly South Korean farmers tried to storm the meeting, police were observing similar gatherings overseas.

In preparation for the Olympics next year, Hong Kong police officers were in Sydney.

'We must keep a high level of awareness,' Mr Tang said.

Terrorism is one of seven areas highlighted in the 2007 Commissioner's Operational Priorities brochure. That underlines the need for co-operation and exchange of intelligence between the Hong Kong Police and its counterparts worldwide, including the mainland. It reminds all officers of the need for vigilance at the airport, on the border and on the beaches to check who is coming in. It calls for constant exercises and changing contingency plans in case of attacks. 'Naturally, I expect the district commander in Central is going to have terrorism at the very top of his agenda compared to the district commander in Kwun Tong.'

It's a strategy of eternal alertness. One of Hong Kong's greatest assets in combating terrorism is the public.

Here police must draw a delicate balance. The public must be aware of the dangers of a terrorist attack, know what to look for and how to alert authorities to suspicions.

On the other hand, police don't want to alarm people unnecessarily. Those seven points in his Operational Priorities, which have gone to every last one of the 27,000 officers, cover violent crime, triads, quick-cash crimes, terrorism, drugs, visitors and illegal immigrants and road safety. The prime responsibility of the force is 'very basic police work'.

Because of politics and geography, Hong Kong has a single police force that covers everything from traffic, village policing and street patrols to commercial crime, narcotics and very sophisticated anti-terrorism. This gives enormous opportunities to officers. 'In some forces overseas, a policeman may face 30 years of patrolling, patrolling, patrolling,' Mr Tang said. 'Here, there's much more scope and opportunity.'

In the first half of this year, of a total of 40,357 crimes, only 2.6 per cent were linked to triads. There's been a downward trend in triad crimes since 1997. Once again, there's no complacency.

'We emphasise different tactics,' Mr Tang said. 'We target triad activities, we have under- cover agents, we co-operate with counterparts in Macau and Guangzhou.'

Schools are a major recruitment ground for gangs. School liaison officers work closely with headmasters. In areas where triads might pressure students to join a secret society, police are stationed in playgrounds.

'We hit their profits. That could be pirated CDs, illegal oil imports, prostitution or smuggled cigarettes. They are a prime target. As a major city with a lot of international economic activities, we've got some organised crime. We keep the lid on it, tightly.'

But policing Hong Kong is much more than fighting crime. It's community relations, lecturing in schools, offering crime prevention services, escorting demonstrations, shepherding the public to the horse races and the Rugby Sevens, controlling traffic, helping tourists and a thousand other tasks.

Some cynical policemen call themselves 'the agency of last resort' and they are right. When some other government agency is unable or unwilling to handle a situation, the public calls the police.

Working relations with the mainland have improved vastly. Mr Tang deals directly with the Ministry of Public Security in Beijing. Police headquarters works on a day-to-day basis directly with police in Guangdong and Shanghai. It's a system that works well and gets results, Mr Tang says. The same applies to relations with foreign forces in every aspect from fighting global criminals to specialist training.

When he was young, an uncle was a member of the Hong Kong Police Reserve, a forerunner of the Hong Kong Auxiliary Police. 'I saw him putting on his uniform,' Mr Tang said. His uncle's stories about duty on the streets gave the teenager an interest in law and order.

A few years later, after graduating from the University of Hong Kong and while an accounts clerk at the Standard Chartered Bank, he applied to join the police.

'There were so many different opportunities in the job,' he said. 'And the pay was better.'

By 1996 he was a chief superintendent. He became deputy commissioner in 2003, preparing to take over from Dick Lee Ming-kwai, perhaps the most admired and respected officer to lead the force. That's a hard act to follow. As he climbed to the upper ranks, Mr Tang continued to study, gaining a master's degree in international and public affairs.

Mr Tang has always been proud to be a policeman. He's now both proud and pleased that one of his three sons, Alex, has decided to follow him on to the parade ground. He's halfway through the nine-month inspectorate course at Police College.

'We talked it through, the special problems he may face being the son of a serving senior officer,' the father said. 'He was sure he could handle them.'

When he marches out of Police College, part of Alex Tang's duties will be doing what generations of policemen have done for decades: he will be in uniform and on the streets.

'You can't beat the sight of a policeman in uniform on the street,' said the commissioner. 'They can see more and the public can see them.

'A policeman on foot gives the public confidence. They catch a high rate of criminals red-handed. Of course they're backed up by police in cars to guarantee a rapid response; we promise that within nine minutes of making an emergency call there will be a policeman knocking on the door.

'To me, that's very important. Anyone who calls for police help deserves a speedy answer.'