Like many Western apps, WhatsApp is banned in Iran, North Korea and Syria. Photo: BBC

“You’d be surprised how many people have figured it out,” Will Cathcart told BBC News.

Like many Western apps, WhatsApp is banned in Iran, North Korea and Syria.

And last month, China joined the list of those banning users from accessing the secure platform.

Other countries, including Qatar, Egypt, Jordan and the United Arab Emirates, restrict features such as voice calls.

But WhatsApp can see where its users truly are, thanks to their registered phone numbers.

“We have a lot of anecdotal reports of people using WhatsApp and what we can do is look at some of the countries where we're seeing blocking and still see tens of millions of people connecting to WhatsApp," Mr Cathcart told BBC News.

'Stop something'

China ordered Apple to block Chinese iPhone users from downloading WhatsApp from the AppStore in April, a move Mr Cathcart calls "unfortunate" - although the country was never a major market for the app.

"That's a choice Apple has made," he said.

"There aren't alternatives.

"I mean, that is really a situation where they've put themselves in the position to be able to truly stop something."

Android users, however, can still download WhatsApp without going through official shops.

But elsewhere Mr Cathcart said the rise of virtual private networks (VPNs) and WhatsApp's proxy service, launched last June, has helped keep WhatsApp accessible.

Suspected criminals

As well as WhatsApp and Signal - both end-to-end encrypted, so only the sender and receiver can read content - China has banned Telegram and demanded the removal of microblogging app Threads.

Mr Cathcart was speaking to the BBC on the last day of the World Service Presents event about internet freedom.

He has long considered the successful export of Western technology platforms key to spreading values of liberal democracy.

But he admits its power is diminishing, along with the Western ideals of a free and open internet.

"It's certainly under threat - and I think it's a struggle," Mr Cathcart told BBC News.

"We take a lot of pride in the fact that we're providing secure private communication that is free from surveillance of authoritarian governments, or even censorship from government, to people all around the world who otherwise wouldn't have it.

"But it is a constant threat and a constant battle."

With its potential ban of Chinese-owned TikTok, for national security reasons, the US has now joined this battle.

And Mr Cathcart was also keen to express concerns about continuing government moves, including in the UK, to ban end-to-end encryption and allow police to read suspected criminals' messages.

"Sadly, I don't think the debate is over," he told BBC News.

"People care about privacy, whether they're aware of end-to-end encryption and what it is and how it works.

"And that's one of the reasons we've had to communicate so much about it, is to be really clear about what it means and what's at stake."