At the height of the cold war clandestine meetings between Americans and Russians were often held in Amsterdam, a heaving city famous for its laissez-faire attitude and genial indifference to foreigners in town for business, pleasure or, indeed, covert liaisons.

“I’ll meet you halfway,” was the code often used to set up those meetings. Then it was simply a matter of flying in for a plausible reason – a boring trade conference, a viewing of some old masters, a romantic jolly to the diamond district or a brief stopover at Schiphol airport.

It still happens. There are two types of liaison. For the first it’s a matter of staging a chance encounter, of the well-I-never- it’s-been-ages type, that can happen in any big city on any day of the week and is over and forgotten about in minutes. Nothing to it. Nobody bats an eyelid.

The other is more onerous. It’s the kind of encounter that nobody can know has ever taken place. Total deniability is a prerequisite. That takes secrecy. And secrecy, unfortunately, requires resources. “Unfortunately” because resources mean that someone or something amiss can easily attract attention.

“A lot of international business is transacted in Amsterdam, which makes it a good place to stage a chance encounter,” Willemijn Aerdts, an intelligence specialist at the institute for security and global affairs at Leiden University, says.

Whether such a meeting is safe depends on old-fashioned “tradecraft” rather than on the type of mass surveillance increasingly associated with intelligence gathering.

“Intelligence services monitor constantly. They look for anything on their patch that stands out as trying to make the unusual look normal, such as patterns of behaviour or encounters that don’t seem to be in line with expectations.”

A meeting between associates of Donald Trump, when he was president-elect of the United States, and Russian officials or go-betweens would certainly have fallen into that category, Aerdts says, and would have attracted the attention of the Dutch security service, the AIVD, had anything aroused its curiosity.

Something did arouse its curiosity, according to the New York Times last week. It raised the temperature in the White House by alleging that European allies, including the Dutch and the British, passed intelligence to the US describing meetings in European cities “between Russian officials – and others close to Russia’s president Vladimir V Putin – and associates of President-elect Trump”.

Those allegations came as Mike Flynn was forced to step down as Trump’s national security adviser after it emerged that he had misled Vice-President Mike Pence and other senior White House officials about his conversations with the Russian ambassador to the US, Sergey Kislyak.

Days later Trump’s nominee for attorney general, Jeff Sessions, faced stormy confirmation hearings after it emerged that he had also held two undisclosed meetings with the ambassador during the campaign.

But how and why would the Dutch intelligence service pass information about such meetings to its US counterpart?

“The Netherlands has always been regarded as a reliable partner of the US,” Aerdts says. “It has worked intensively for a long time with the American intelligence agencies. As a result several partnerships would exist when it comes to the exchange of classified information.”

The Five Eyes

At the next level are the Nine Eyes – Germany, the Netherlands, France, Belgium, Denmark, Italy, Spain, Norway and Sweden – which have formed a similar alliance, giving the Five Eyes additional reach.

The combined network is known, as you might guess, as the “14 Eyes”.

“It’s a hidden empire,” another NSA whistleblower, Thomas Drake, says.

How have the West’s geopolitical rivals, particularly Russia and China, reacted to this extraordinary intelligence behemoth whose operations and facilities cover all time zones and all continents?

The hard fact facing Moscow, Beijing and, arguably, Tehran is that this is a western intelligence monster that is impossible to replicate. Even were it technically feasible the cost would be unimaginable.

“It takes a long time and a lot of expertise and money to create the mechanics needed to build a relationship that is so elaborate,” Gregg Fyffe of Ottawa University says.

One fear is that the Russians and the Chinese have responded to the West’s collect-it-all mentality by deciding to hack it all – hence the concerns that Russia may somehow have compromised the US presidential election and is planning to do the same in the Netherlands, France and Germany this year.

So real is that belief in the Netherlands that the government has decided to turn the clock back almost a decade and count votes in next week’s general election by hand. That in itself is an extraordinary admission about the new policy of technological containment in which the West and its adversaries are locked.