Jenny Tian, 29, a comedian from Australia, had been in London for two weeks when she saw a group of guys in ski masks on a street in east London. “I thought to myself: ‘They’re probably on their way to rob a home, they’re not going to bother me.’” It was 5pm, still broad daylight, and she had her phone out, trying to find a venue on Google Maps. “You know when you’re turning yourself into a human compass, pivoting around, trying to work out where it’s sending you? I looked very lost, I guess.” The next thing she heard was the sound of running, then a whoosh of air, and her phone was gone.

This was not OK. London’s first independent victims’ commissioner, Claire Waxman, stressed in a statement that she definitely gets it. “Our lives are on our phones – our contacts, family photos, social media accounts, contactless payments, travelcards, emails. They are a form of safety and comfort for people but taking someone’s device robs them of that security.” For Tian, there was weeks of work on her phone – notes for her standup, edited videos for her Instagram feed, all her contacts with bookers, all her connections to home, her Apple Pay, her banking details, her diary, never mind she didn’t know where she was.

Vaneet Mehta, 32, a software engineer, works from home, and has to log in through a VPN, which she cannot do without her authenticator app. So when her phone got lifted, at some traffic lights in north-west London, the first thing she had to do was call work to take the day off. Except she couldn’t, because she didn’t have a phone.

We used to joke about screen time, that as a species we had managed to invent a device containing the whole of human knowledge, and then we expect each other not to look at it. But knowledge isn’t the half of it; our phones have become the repository of all our practical interactions with the world. Numerous people described suddenly losing their phone as like being struck blind.

Phone theft is a growing global problem, but in UK terms it’s predominantly a London problem. Government figures published in September showed that “snatch thefts” had gone up by 150% on the year before. And of the 78,000 people who had had a phone or bag snatched in England and Wales in the year up to the end of March, more than 58,000 of those (74%) were in London. That the capital is the centre is no surprise, says Dep Supt Saj Hussain, the Metropolitan police’s lead officer for phone theft. “It’s the largest metropolis, it’s the area that most people come to visit both nationally and internationally. It’s got a lot of footfall, especially tourists. We have some of the best transport networks in the world in London. The Elizabeth line has been wonderful for me to commute, but it’s also a wonderful opportunity for those that have been committing thefts elsewhere to come into London, which is a more lucrative market. It’s the opportunists’ capital of the nation. You can’t change that.”

Hussain calls losing a phone, simply, a “trauma”, and I get that. What surprised me was what he said next: “You must call 999 immediately.” Seriously? Haven’t emergency services got more important things to do? “The core police doctrine, which we all work towards as officers, is to prevent crime, save life and limb, and keep the peace,” Hussain replies. “And yes, these thefts fall within that.”

It sounds weird only because urban legend says the opposite: the TalkTV presenter Mike Graham wrote that he reported a phone theft in person to a police officer, who replied that his own phone had been snatched the week before while he was in uniform, and the best thing to do was fill in an online form.

Elysia, 27, was down in London from Glasgow doing an internship. She was on the tube, and a guy lifted her phone an instant before the doors closed, then sped out and vanished like a ghost. Although dismayed, she had to grudgingly admit how impressive it was. “He would have taken gold in the phone-snatching Olympics,” she says. Elysia wouldn’t have gone to the police at all, except that she couldn’t get past the tube barriers without her phone, and the staff called the police.

Lina Slim, 39, experienced two attempted phone thefts in the space of three weeks, and still says: “When a passerby said: ‘Let me call the police for you,’ I thought that was a bit extreme.” Many people only call a couple of days later, needing a crime number for the insurance claim, but there’s a golden-hour principle: not only are the police much more likely to catch anyone in the area if they know within 60 minutes, they’re also more likely to recover CCTV footage. “These offenders aren’t people who are likely to be taking one phone,” Hussain says. “They’re opportunists.” A team that catches up with a scooter might find a whole bag of phones but, as people who track their stolen phone using an AirTag or Find My Phone attest, they can move across a city at lightning speed, and out of the country – often to China – in a day or two. So when you see headlines saying only half of phone thefts are ever investigated, it is largely because they were called in too late and there was no point; yet figures like that put people off reporting their theft, so under-reporting and underinvestigating are in a feedback loop.

Tian gave chase. “I wasn’t going to let this guy get away with it. I’m from Australia, where this is not a cool thing to do. I was yelling: ‘He’s got my phone! Don’t let him get away!’ I don’t think he was expecting me to be so loud and aggressive.”

“Leave the policing to the police,” Hussain advises, with gravity. According to the Met’s figures, a quarter of London snatch thefts are knife-enabled. “The victims of that are predominantly school-age children,” Hussain adds, soberingly.

So what happens next? In the best-case scenario – which Daniel, 56, describes – your phone is rubbish. “Out of nowhere, this chap suddenly appeared, on an ebike, going at some speed. He grabbed it strongly and whisked it away. I didn’t even shout. It was immediately pointless; he was 10 yards down the road before I’d even realised what had happened.” But because Daniel’s phone was old, the thief then dropped it, and a bunch of teenagers brought it back, screen smashed but otherwise in one piece. Slim managed to keep hold of her phone the second time a snatch was attempted, and says that now, “whenever I see teenagers on bikes, I always cross the road. Sometimes I’ll take a longer route just to avoid passing them.”

Stolen phones usually get sold overseas or domestically, at small pop-up stores, Hussain says. But the police don’t really know what networks thieves are using. “That’s the intelligence gap we need support with, both from our own teams and from victims.” As part of a crackdown announced in September, the government is launching a nationwide probe into the stolen phone market, and is planning a summit with manufacturers and tech companies to develop new anti-theft measures.

At the Met’s educated guess, though, stolen phones are usually sold on for less than a tenth of their value. They’re easy to move and make untraceable – “whether it’s by the unsophisticated model of covering them in silver foil [so that they can stay on but not transmit their location], or that they’ve been able to switch it off”, Hussain says – but, in theory at least, they should be very hard to repurpose. Target-hardening – destroying the market by making the phones useless – is a work in progress by phone companies, and they’ll never be able to destroy the value completely. “Every part of the phone is a valuable component,” Hussain says. “On the new iPhones, it’s a couple of hundred pounds just for the screen.”

If you’re insured, that’s something; if you’re not, you’ll just have to stump up for a new phone. There’s an additional layer of anxiety if you have set up Apple or Google Pay, and Elysia was worried that the thieves could have guessed her pin, “but even if they’d got into my bank account, there was very little they could have got out of it”. The asymmetry of how much it costs you, in money, time and emotion, versus what it yields to the thief, is galling.

“It was such a rubbishy cheap phone,” Elysia says, “because I’m such a rubbishy cheap person, that they wouldn’t have got anything for it anyway. It did epitomise for me everything that feels a little bit grim about London. This epidemic of phone-snatching can only really be produced by awful wealth disparity, the unmanageable hugeness – he’ll have already vanished, once he’s out of the station he’s gone for ever – the weird atomisation of everybody living there which basically means that people can rob very visibly with no repercussions.”

Many people also cite ebikes as a factor, by-the-minute hires such as Lime that can accelerate getaway speeds, but the Met estimates that only 3% of snatch thefts are by moped, 6% by pedal bike. It’s possible that the feat of this kind of theft is so memorable that people tell more vivid stories about it.

So, how do you protect yourself against it? “Be aware of your surroundings,” Hussain says. “Look up, look out. Use your pin services better. Keep phones and watches and cash out of sight.” Mehta now only ever checks her phone with her back against a wall and two hands on it. Another former victim says they now instinctively put an index finger over the top of their phone when they’re out, making it harder to whisk it out of their hand. “Plan your route home,” Hussain says. “Put a tracker app on your phone – Find My iPhone isn’t that specific metre-by-metre.” It is still useful, though, as you can mark your device as stolen remotely and render it unusable.

A spokesperson from O2 recommends the following, before it’s stolen: make a note of the IMEI number, your handset’s unique reference, then the police can get it back to you if they find it; make sure your banking apps, particularly, have a different passcode to the phone itself, as some thieves do “shoulder-hanging”, where they watch you unlock the phone and then snatch it; if you go into settings, you can put a pin on your sim card, so if a thief tries to put the sim in a different handset, it’ll be protected; turn off message preview, so that authentication passcodes won’t be visible without unlocking.

After the phone is stolen, report it as soon as possible, since networks will cap your losses – say, if a thief racks up a lot of international calls – but only if you’ve notified them within 24 hours. All UK providers have an agreement to “brick” a phone – which means it can’t access any network – but where it gets tricky is if the phone ends up in China, as they frequently do. Also, bear in mind that 80% of snatches are of iPhones.

Daniel, who got his phone back, went back to Wallasey with his view of crime unchanged, “overall, rationally. You just realise crime is real.” Slim held on to her second phone and still has it. Elysia says: “It’s less that it changed my opinion of London, it was more that it confirmed what I didn’t like about it already.” Mehta says: “The nerves have mostly worn off,” but she has changed her settings so that the phone can’t be turned off unless it’s unlocked.

As for Tian, after hollering and chasing her phone thief, “pedestrians started cornering him, and eventually he ran out of places to hide. He sheepishly handed it back to me, then he joined his group of boys again, with the ski masks. Then the people who helped me out walked me to the bar I was trying to get to. I was basically like Snow White; a bad thing happened but everyone seemed to help me out. They were very kind. My impression of London is that everyone is so nice. Even the guy who stole my phone handed it back to me.” As heartwarming as it is, this is a rare exception and, emphatically, not the advice of the police. It’s dangerous. It might mean everything to you, containing as it does your entire world, but it’s only a phone.