John Lee, a former beat cop who became Hong Kong's security chief and played a key role in suppressing democracy protests, became the business hub's new leader on Friday in a ceremony overseen by Chinese President Xi Jinping.

"It is the greatest honour for me today to shoulder this historic mission given to me by the central authorities and the people of Hong Kong," Lee said in his inauguration speech, thanking Beijing for its support.

Lee, 64, was anointed as Hong Kong's next chief executive by a small committee in May, winning 99 percent of the votes in a choreographed, Beijing-blessed race in which no other candidates stood.

Xi later said Lee's government would deliver a "new chapter" for Hong Kong.

Lee's elevation caps a remarkable rise for a man whose police career lifted him from a working-class family to the upper echelons of Hong Kong's political establishment.

It also places a security official in the city's top job for the first time, a man who was pivotal in the quashing of huge democracy protests in 2019 and Beijing's subsequent political crackdown.

Insiders say Lee's unwavering commitment to that role won China's confidence at a time when other Hong Kong elite were seen as insufficiently loyal or competent.

"John Lee is the one that the central government knows the best, because he was in constant contact and interaction with the mainland," pro-establishment lawmaker and prominent business figure Michael Tien told AFP earlier this year.

Lee, who is under US sanctions, spent 35 years in the police before jumping to the government in 2012, followed by a swift rise to the top.

Law and order remained his portfolio, with him serving in the Security Bureau and then leading it before becoming the city's number two official last year.

Lee, a Catholic, grew up poor in Sham Shui Po -- one of wealthy Hong Kong's working-class districts -- but made his way to an elite boys' school run by Jesuits.

Peter Lai, a former banker and classmate, described him as a clever and fashionable teenager who grew long hair and wore flared trousers.

Most of his contemporaries went to university, but Lee turned down an offer to study engineering to join the police.

John Lee swore his oath in front of Chinese president Xi Jinping
John Lee swore his oath in front of Chinese president Xi Jinping POOL via AFP / Selim CHTAYTI

He later told a pro-Beijing newspaper he was motivated by being bullied by neighbourhood hooligans.

Two former classmates gave a more practical reason -- the police force offered a stable career for Lee and his pregnant wife Janet.

Lee has not spoken much about his family and has dodged questions about whether his wife and two sons still hold British nationality, something he renounced when he joined the government.

As events began on Friday morning, Lee's new social media accounts posted a picture of his wife fixing his tie, thanking her for "silently supporting me and taking care of the family over the years".

Given his security background, it seems unlikely Lee will reverse Beijing's campaign against dissent.

Where he will enter less familiar territory is the world of business.

Hong Kong, once a vibrant, multicultural business hub, has been cut off internationally during the pandemic as it shadows Beijing's strict zero-Covid strategy.

Its economy is struggling and there has been an exodus of talent.

Danny Lau, a small business association leader, said Lee was not an ideal candidate but that he would reserve judgement.

"I hope he can consider Hong Kong's international competitiveness and does not waste time on making laws unhelpful for the city's economy," Lau told AFP.

But others say Lee's appointment confirms that China now puts Hong Kong's political security ahead of business and livelihood issues.

"In the past, China might compromise for some economic benefits," Charles Mok, a former pro-democracy lawmaker now living overseas, told AFP.

"But now it seems Beijing wants its people to feel that the world is full of threats and it's only safe to stick closely to the (Communist) Party."