The security guards have the whole place fenced off like a crime scene. Periodically, a manager walks to the edge of the cordon and genuinely utters the immortal line to the waiting crowd: 'Nothing to see here. Move along now.'

The assembled throng – entirely comprised of young men, most in hats or hoodies – have little intention of moving on. They are not menacing but there is, nonetheless, a sense of repressed confrontation.

We may be in the throes of a shoplifting epidemic but this lot are not here to pilfer. They're here in this corner of Britain's largest shopping mall to do some shopping – and they know there's stock inside the shop.

The problem is that the shop is not selling any of it for fear of a stampede, while staff await orders from head office on how to release the merchandise safely.

In years to come, I dare say scholars of psychology, of marketing and of media studies will be writing research papers on the bizarre phenomenon of the Royal Pop watch.

This is a new watch range created by the unlikely union of Swatch, the mass-market, cheap-and-cheerful watch brand and Audemars Piguet, the ultra-exclusive 150-year-old grandees of Swiss horology.

The former churns out reliable, multi-coloured plastic wristwatches for less than a pair of jeans. The latter produces handcrafted timepieces, costing upwards of £30,000 for an entry-level 'AP' model. The new hybrid is a blend of Swatch's 'Pop' range and AP's classic 'Royal Oak' design.

In automotive terms, it is like an alliance of Bentley and Kia. Foodwise, think Fortnum's hooking up with McDonald's. If watches were human, this would be a princess-snogs-barman story. You get the drift.

And over the weekend, the progeny of this unexpected tryst was launched at Swatch stores around the world with a £335 price tag and astonishing results.

From Singapore to Liverpool, vast numbers of would-be buyers turned up to grab one of the first specimens. The pandemonium reached the point that police dogs were summoned to the Swatch shop in London's Battersea Power Station, chairs went flying in Manchester, a dispersal order was issued in Birmingham and tear gas was fired in Paris.

A quick glance at the internet explains why. Some brand addicts and logo junkies simply want to have a watch with the revered 'AP' logo for a tiny fraction of the usual price. Others, however, want to make a fast buck.

Within hours, some of those who did reach the tills were already listing their purchases online at four times the list price. This is why police were summoned to several Swatch stores in the UK on Saturday before the company decided to bring the shutters down everywhere later in the day.

The Royal Pop comes in eight models, from a sober black and white number, the Ocho Negro, to a bright pink/yellow/green model which reminds me of something my children picked out at Peppa Pig World years ago (it's actually called the OTG Roz).

Last night, a complete set of all eight versions was sitting on eBay for £34,000.

Adding to the peculiarity of it all is that these are not wristwatches but pocket watches, the sort we associate with period dramas – attached by a chain to the waistcoat of an elderly gent.

The Royal Pop, however, has no chain. It hangs around your neck by that dreariest of managerial accessories – a lanyard (albeit a colour-co-ordinated calfskin one). 'This collection will change the way we wear watches,' boasts the blurb from Swatch, 'allowing you to wear the watch in unexpected, playful and dynamic ways.'

On paper, to those of us who, like me, use a phone to tell the time, the entire concept sounds baffling. I cannot envisage paying £335 for a clunky bioceramic pendant with a clock on it. But, hey, there's no accounting for taste.

Which is why a couple of dozen young men are loitering by the security railings outside the Swatch shop at Westfield White City, in West London.

Monday lunchtime is usually quiet but not here next to Aroma Zone and above Whistles. Several guards in stab vests are policing the walkway. 'When you gonna start selling?' a young bearded man asks a manager who's emerged to issue another reminder that there'll be no Royal Pops sold today, pending further instructions from head office.

The only way to gain entry to the shop is to buy something other than a Royal Pop.

When I say I want an ordinary Swatch, I'm greeted like a long-lost relative. 'At last, someone who wants a normal watch!' exclaims the assistant. I have the whole place to myself as I browse a selection of cheap and cheerful models and pick a straightforward black thing with a plastic strap. It has a second hand and gives me the day of the week and the date. That's more than the Royal Pop can do, and my purchase is a sixth of the price at £53.

'It was crazy over the weekend. People had been camping out all night. We never got round to selling a single Royal Pop because we couldn't open,' says the assistant.

What happens next? 'We're waiting to be told what to do. People just need to look at the social feeds.'

Back at the barriers, I meet 'Deepjon', who was among those who camped outside this shopping centre on Friday night. His plan was be near the front of the queue on Saturday and was furious to be met by locked doors. How come he is still here? 'I'm at college and I've only got one exam left,' says the computer science student from Ealing. 'I just want the money.'

One young self-appointed leader of the pack addresses the others. 'Look, guys. They'll only start selling if we disperse, so let's all go round the corner,' he suggests. The rest of the gang are not buying that, so everyone just hangs around sulking and waiting for something to happen.

Business may be slow to non-existent but the Swatch bosses are delighted by the attention. 'This new collaboration is literally making social media explode, with over six billion views within one week,' the company tells me by email. 'Now it is already 11 billion. All in all, the Royal Pop Collection is captivating the entire world.'

One wonders what's in it for Audemars Piguet, though. Started by two Swiss boffins in 1875, it is widely regarded as one of the four grandest watch brands in the world. Its 'Royal Oak' design is based on a royal/nautical theme (unusual perhaps for a landlocked republic).

Having spent a small fortune for the exclusivity of an Audemars Piguet original on their wrist, 'AP' loyalists may wonder why they're now to be joined by thousands of bargain-hunters in lanyards.

The upper tier of the horological community is split. Some fear 'AP' has 'trashed the brand'. Others argue this is an ingenious move to encourage a new, younger crowd to enter the world of watch collecting.

Before they do, they should grasp one of the fundamentals of collecting. Both companies involved have stressed that these are not limited-edition watches –everyone will be able to spend £335 on a Royal Pop ticking lanyard in time. But then, many of those laying siege to their local Swatch store were not terribly interested in telling the time in the first place.