Deep beneath the Atlantic Ocean, forgotten for the best part of a century, lies a tunnel linking London and New York.
It was built on the whim of a Victorian inventor with the aim of linking two great cities and developing the kind of friendship that still exists today.
Until today, that is, when the project was rekindled with a modern twist.
Using a giant "electronic telescope" and state-of-the-art technology,
It meant that New Yorkers and Londoners could wave to each other across the sea and begin the kind of mute dialogue that was only a dream all those years ago for eccentric engineering entrepreneur Alexander Stanhope St George (deceased).
Or at least, that's the way the story goes.
And - oh dear - it didn't take us Brits too long to utilise it for a bit of fun at the expense of our American cousins.
First there was the chap unbuttoning his shirt for an interested party on the other side.
Then came the group whose hand-held banner urged an assembly of curious New York cops to hop on one leg (which, incidentally, they declined).
Goodness only knows what everyone will get up to when darkness falls. But artist and creator Paul St George is delighted that this reworking of his great-grandfather's project is helping to spread a little happiness.
It takes some while to grasp the concept of the Telectroscope, unless you're happy enough to accept as gospel the story behind its creation.
According to the publicity material being handed out yesterday, the original tunnel was pioneered by an orang-utan running its entire length in a safety test before disappearing with the wife of the New York City mayor. Perhaps you get the picture now.
The truth is that the Telectroscope - installed by Artichoke, the same people who spectacularly paraded a mechanical elephant through London two years ago - probably employs the latest broadband, camera and satellite technology to close the gap between our two great nations.
Anyone you asked today, however, simply put it down to magic.
The Telectroscope uses 6ft screens and a Jules Verne style telescope that gleams with brass and an array of Victorian dials. Participants peer into one end of the screen - and hey presto - they can see anyone standing at the other side.
Much of the first few hours of this morning were taken up by bemused-looking Americans gazing cautiously at the antics of the London transatlantic gazers before realising that it wasn't a set-up, that they weren't being filmed for a candid camera TV stunt, and that it wasn't a terrorist threat.
One of them broke the ice with a message they must have thought was a subject close to British hearts - the weather.
"Raining here!" said the Yank's handwritten note, pressed tentatively to the screen. "Sunny here!" replied a trio of blondes in London, before fanning their faces and performing heat-wave actions in mime.
Jewellery company worker Annie McDonald, from North London, exchanged kisses at a stranger standing beneath Brooklyn Bridge after beginning a semaphore style conversation with him.
I tried it with a 30-something who looked as if she was on her way to work - but she just giggled, pointed to her watch, and disappeared from view. Ho hum. That's the thing about Telectroscope flirting - if you don't fancy it, you can just step aside.
So unless you happen to find someone in Brooklyn who can lip-read, it's impossible to talk the talk.
But you can still chalk the chalk. Thus, with the used of a liberated restaurant blackboard, I tried a transatlantic conversation with Todd Glass, 41, who was pushing his five-month-old son Simon in a buggy.
He assured me he was not a hologram - but, crucially perhaps, was unable to tell me who the next President would be. So was he really real? "You bet," he replied.
Andy Slater, 28, from Edinburgh, visited the Brooklyn screen with his girlfriend Sarah Cook, 33, from Newcastle-upon-Tyne. The message from these Brits abroad was classically simple: "Send Tea!"
Visitors to the Telectroscope web site - www.tiscali.co.uk/telectroscope - have already revealed online that they will use its wizardry to bond with friends or relatives abroad, show off an unseen grandchild to grandparents in New York, and - who knows - maybe even to propose marriage.
One couple plan to use it so their Manhattan friend can flick through brochures of apartments they are trying to rent.
"Part of the idea is just to allow people to use it in whatever way they want," said Mr St George, 53, from Bristol, who insists he developed the Telectroscope after discovering his great-grandfather's dusty notes and diaries in an attic.
"The thought of a tunnel under the Atlantic is fascinating," he said.
"What child has never dug a hole at the beach and wondered how long it would take to go through to the other side of the world?
"The Telectroscope is a stage, and the people who use it are the performers.
"Their unpredictability is all part of it. It's encouraging people think about different ways of communicating, to see people living everyday lives thousands of miles away - and, perhaps, to study the way everyone reacts differently to something they're not quite sure about."
As we speak, another group of NYPD cops pulls up at the Brooklyn end in a squad car with flashing red lights.
At first they give only wooden waves to the Brits assembled at Tower Bridge. Then one of them - dressed in uniform and packing a handgun - is encouraged to assume a cowboy-style pose. Across the Atlantic, an unheard cheer goes up.
The cop becomes an instant hero. Here's lookin' at you, kid...