Hong Kongers became the fifth largest foreign investors in central London as of last August and have been driving up prices in some popular districts outside the UK capital.

But the new wave of buying also includes some Hong Kong residents who are pooling money to invest, a trend property agents expect to continue as more middle-class Hong Kong residents consider leaving for Britain and look to establish a source of revenue in advance.

"It's become much more of a trend in the past six months or so," Guy Bradshaw, head of London Residential at Sotheby's International Realty told Reuters. "I've certainly been involved in a lot more conversations and Zoom calls with people in Hong Kong and funds in Hong Kong."

The UK government is offering a new visa to Hong Kong holders of British National Overseas (BNO) passports that gives them a chance to become British citizens - a change it made after China's national security law for Hong Kong.

A steady rental income would be useful in applying for the citizenship, as the BNO holders need to prove they can provide financial support for themselves for at least six months.

London estimates that over 300,000 Hong Kong residents could emigrate over the next five years, and Bank of America expects Hong Kong residents moving to Britain could trigger capital outflows of $36 billion in 2021.

While Hong Kong residents have long been active buyers of homes in Britain, real estate agents say more recently there has been increasing interest in older apartments and houses as rental assets.

Hong Kongers have an affinity for real estate investment, with property prices in the Asian financial hub among the most expensive in the world.

Alan Wan, 38, who owns 13 residential properties in Britain, launched classes in Hong Kong two years ago - at the height of anti-government protests in Hong Kong - aimed at potential investors in properties in and around Manchester.

So far, his "UK Property Owner Association" class has attracted around 1,500 students. Enrolment spiked in the second half of last year after Beijing imposed the national security law.

One of Wan's students, 30-year old Isla Kwok, who moved to Manchester in late January waiting to start a degree, is using the rental income she receives from a terraced house bought in 2019 to finance the cost of renting a smaller flat and mortgage payments.

She plans to re-mortgage her first property to buy a second one this year after getting a residence permit, as mortgage interest rates will be much lower.

"Once you've started your first property, it's much easier to create more income to ease the financial pressure of living here," Kwok said.

Wan said most of his students bought their properties individually, but he also had some who pooled money to buy in London.

Marc von Grundherr, director at realtor Benham and Reeves in London, said he has seen the same trend.

"I've had a few clients come to us and say, 'Look, my son or my friend is wanting to invest in property because they're thinking about coming (to Britain), but they can't afford to do it on their own or they want to buy something slightly different - is it okay with two or three or four of them buying together?"

"That's a change. Obviously you always had larger investment companies who bought large amounts of stock, but we're talking not the very, very, very wealthy," von Grundherr said.

(Reporting by Clare Jim in Hong Kong and William James in London; Editing by Jacqueline Wong)

By Clare Jim and William James