During July and August, wealthy African families travel to London — the world’s most popular city for second-home ownership — to escape the heat in their home countries, TheGuardian reports.

They may have helped push up the number of London millionaires to 191,000 — data provided from the wealth management arm of Barclays Bank.

The number of millionaires in the U.K. rose by 41 percent over the past five years, with one in 65 adults now having seven-figure bank accounts thanks to booming house prices and stock market gains, according to TheGuardian.

The average price for a London home is £432,000 ($664,243 US), according to London24.

But there’s other research that suggests Barclays’ London millionaire figure is too low, TheGuardian reports. Wealth consultancy WealthInsight says London is home to 289,500 millionaires — one in every 28 people — and probably more if you include wealthy families from other countries who own second homes there.

The question is, how many Africans are among them, and will they help share knowledge and build businesses back home?

These were some of the questions posed Thursday by Donovan Neale-May at the SA Innovation Summit in Cape Town. Neale-May is managing partner at Sable Accelerator, a kind of global match-making service for African business people and Africans in the diaspora.

Sable connects with Africans in the diaspora who want to provide support in the form of funding, access to markets, management support, technical assistance or any other help they need, TheCitizen reports.

These are some of the ways Africa’s brain drain is being reversed, Neale-May said.

South Africa’s estimated 1.2 million expats and emigrants around the world represent a vast repository of experiential knowledge, Neale-May said. South Africa has an asset in the diaspora — an intellectual capital base outside the country.

Neale-May left South Africa decades ago, building successful businesses in the U.K. and U.S. He maintained his ties with Africa as many do, TheCitizen reports.

More than half of Silicon Valley startups were launched by immigrants, including many South African entrepreneurs who moved there to gain access to capital, leading developers, excellent feedback and the various other benefits of being in a global innovation hub, according to TheCitizen.