It is shortly after 8am on the South Bank in London, but something has gone a little awry at the cutting edge of technology. In a plaza next to the London Eye, a handful of men in their 30s and 40s are standing around a bright yellow box the size of a vending machine, forlornly pressing its buttons to little effect.

Before long a group of black-clad PR types have erected a yellow tent over the device, behind which an engineer busies himself. “Oh, there’s no issue,” says one cheerfully, “the Snapbot is just having a little nap. He’ll be awake soon.”

Appearances might, for the moment at least, be underwhelming, but to those in the know (for which read gadget-loving millennials), this was supposed to be a significant moment in wearable technology.

Snapchat, the photo-sharing app beloved of technophile teenagers and young adults, is launching in Europe its first foray into tech hardware – a pair of sunglasses into which a tiny camera and microphone is embedded, allowing users to grab 10- to 30-second bursts of video and send them as messages to their friends across the network. Named Spectacles (note the capital S), the glasses were launched in the US in November, as part of what the company hopes will cement its position as the cheekily innovative nephew to what it likes to regard as its more uptight relatives Facebook and Twitter.

“Snapbots” (the vending machines) have duly appeared overnight in Berlin, Paris and Venice, but on the basis of the London launch, the word of mouth buzz that saw long queues in the US is taking a little while to build. Happily, by the time the problem is resolved around 9am, and the machine starts spouting glasses through its smiling mouth in exchange for £129.99, enough eager early adopters have gathered to constitute a small, if still all-male, queue.

One of them is 32-year-old Chris Walts, who works in advertising and says he has been following Spectacles since they launched in the US. “I just really like to play with the new technology. I like the aesthetic, it’s fun, it’s clever and it just looks like something you would like to put on your face.”

That view might not be shared by everyone. The styling of the glasses might kindly be described as goofy, particularly in their migraine-inducing blue or coral versions (they also come in black). But with their conspicuous design and a light that flashes while users are filming, what they are not is surreptitious or po-faced – two of the criticisms which sank Google Glass, the tech firm’s attempt at spectacle cameras which stopped production in 2015 after two years.

Shane Dillon says he spotted news of the launch on Twitter and decided to secure a pair because “they’re a bit of fun, and it’s on my way to work”. As a civil servant in his 40s, Dillon is not exactly Snapchat’s core demographic, and he admits that he is hardly a heavy user of the network – “maybe two people might view my snaps”. Truthfully, he says, he relies more on Twitter for news, but he couldn’t resist trying the glasses for himself.

“They will probably be in a drawer by August or September, but for the summer I’m going to have some fun with them.” What sort of things can he see himself filming? “Well I have two cats, so I’ll probably be filming them all weekend.”

Snapchat was launched in 2011 by a group of former students at Stanford University who struck on the idea of a network based around sharing photos that automatically deleted once read. Initially dismissed by critics as a tool for sexting, its flirtatious but disposable messaging style captured the imagination of young users who found Facebook too stuffy.

Though still dwarfed in size and value by Mark Zuckerberg’s predecessor, Snapchat now claims 158 million users every day; when it launched in March on the New York Stock Exchange it was valued at more than $20bn. But its huge success among advertiser-friendly teens and millennials has made Snapchat’s innovations a target for competitors. Many of its features have been directly copied by Facebook, particularly for its own photo network Instagram, and investors have become nervous about Snapchat’s rate of growth.

For some, however, the network is doing everything right. Phillip Caudell, who is 25 and works as a product designer, was in bed when he spotted news of the Snapbot on Twitter, got dressed and jumped on his scooter to the South Bank (“That’s the quickest I have ever got ready”).

Caudell has been jealous for months of his American friends who have the glasses, he says, since he “[lives] in Snapchat”. After a short wait, he gets to the front of the queue, and secures his Spectacles in coral (“Oh my God. Oh my God”), before promptly taking out his phone to pout for a selfie. What will he use them for? “To be even more irritating to my family and friends.”