The Band of the Irish Guards had just concluded their march through the stately gates of Buckingham Palace when Diego Galdino sprang into action.

From about thirty yards away, among the crowd of tourists eagerly watching the Changing of the Guard, Diego noticed a man and woman whose faces seemed all too familiar.

Without hesitation, Diego dashed down the steps of the Queen Victoria Memorial, navigated across Constitution Hill, slipped beneath the iron railings, and thrust a GoPro camera towards them.

He began loudly proclaiming his renowned catchphrase, “PICKY-POCKETS! WATCH OUT! PICKY-POCKETS!”

What ensued was a bizarre ten-minute spectacle, with Diego filming himself as he trailed the pair through central London, dogging their steps while shouting accusatory questions. “Why are you here again, stealing? How can you have no shame?”

Periodically, he blew a whistle, akin to that of a football referee, to draw the attention of onlookers. “Be careful, everyone! A pickpocket is on the move! Mind your belongings! Watch out for this thief!”

Following Diego’s journey through Green Park and up Piccadilly is a bit like watching an open-air Christmas panto.

Onlookers hiss, boo and jeer at the male ‘picky-pocket’, who tries, with limited success, to cover his face. Diego buzzes around, like an aggravated bluebottle, waving his GoPro, barking out questions and shouting insults. Sometimes his fists are clenched and angry words exchanged. And all the while, as we enter Green Park Tube station and head for the Jubilee Line platform, Diego’s camera is rolling.

Diego Gardino (pictured in front of Big Ben) is on a one-man campaign to expose the petty thieves plaguing London’s tourist hotspots

By the time this alleged crook has escaped, barging his way onto a train and then pushing Diego out of its closing door, we’ve not only filmed more than enough footage to make another viral film, but have also made a passenger’s day. ‘Look!’ he tells his girlfriend. ‘It’s the Brazilian pickpocket guy!’

Diego Gardino is a 32-year-old Deliveroo rider whose one-man campaign to expose the petty thieves plaguing London’s tourist hotspots have turned him into a social media sensation.

On YouTube, where he began posting in July, his ‘@pickpocketlondon’ videos have clocked up more than 20 million views. On Instagram, he boats 330,000 followers. One of his TikTok clips, showing a middle-aged Eastern European woman reaching into the rucksack of an Asian tourist, has been watched an astonishing 27 million times.

Lately, Diego has developed a signature move – he covers the most prolific thieves in red paint.

The other day, he filmed himself letting fly with a spray gun at three women outside the Ministry of Justice in Westminster, shouting: ‘Picky-pockets! Picky-pockets! Today, you’re not going to steal any more.’

A few days later, he taunted a roly-poly thief on Jermyn Street, shouting ‘no more stealing today’ while covering him in red paint. The man pursued him past the Ritz Hotel, puffing and panting while Diego escaped on an electric bike.

Perhaps the most entertaining example of this genre ended with a confrontation on Westminster Bridge, in the shadow of Big Ben, where a woman he’d filmed reaching into a tourist’s handbag reacted to being ‘painted’ by throwing her own handbag at Diego, who cycled off, giggling. Such exploits have, it’s fair to say, divided public opinion.

To his millions of fans, Diego is a bona fide hero on a noble mission to restore law and order to a city where ‘thefts from a person’ increased by 28 per cent last year, to more than 100,000. Some have dubbed him London’s version of Batman. Others say his videos represent the most effective means of shaming criminals since we abolished the stocks.

Critics argue that street justice is only one step removed from mob rule, accusing Diego of not just displaying a cavalier attitude towards the data protection of accused criminals he shames across the internet, but at times coming close to committing assault.

Criminologist Jennifer Fleetwood recently told the AFP news agency that he was committing ‘a performative form of crime vigilantism for clicks’. Whoever is in the right – and it’s possible both sides are – it takes only a few hours in Diego’s company to establish that the streets around London’s most iconic landmarks have become, as he puts it, a ‘paradise for pickpockets’.

We meet at Victoria Station at 11am. Diego fastens a video camera to his lapel, takes another in his hand, and leads me on a whistle-stop tour of his favourite hunting grounds.

They range from the station concourse, where gangs target tourists arriving on the fast train from Gatwick, to bus stops outside, where they look for groups of bewildered new arrivals.

Diego has developed a signature move – he covers the most prolific alleged thieves in red spraypaint

While pickpockets dress like tourists to blend in, they usually carry umbrellas, jackets or shawls over their arms, he explains, to hide their accomplice’s hand as it dips into a victim’s handbag.

‘They are everywhere. They are in train stations, in bus stations, they operate inside the Underground, they go in stores and supermarkets,’ he says. ‘Whatever is valuable to them, that they can take fast, they take it then hand it onto an accomplice. By the time someone realises their wallet has gone, it will have passed through three or four hands and vanished.’

The most productive spots are, of course, the most crowded ones. To that end, the only place to be on a Wednesday morning is outside Buckingham Palace, where hordes of backpack-carrying tourists are corralled onto small patches of pavement behind metal crash barriers.

Diego’s time working as a delivery driver has given him an extraordinary ability to spot criminals at work. We briefly follow a woman in a long sheepskin coat (‘she’s wearing sunglasses on a cloudy day, which is often a sign of the pickpocket’) before moving to an elevated spot where Diego uses the zoom function of his phone camera to scan the crowd.

Suddenly, he spots familiar faces: the aforementioned woman and man, who he caught in the act of stealing a couple of weeks back, and duly ‘painted’. In a flash, the softly spoken Diego morphs into his online alter ego: a shouty vigilante consumed by righteous indignation. The ensuing scenes teach me two lessons.

First, the Metropolitan Police (on whose watch, the Borough of Westminster has seen reported ‘thefts from a person’ almost double to 32,000 in three years) can be woefully lackadaisical about the old-fashioned business of apprehending crooks.

At one point, Diego informs a high-viz-clad policewoman that the couple walking away from him are ‘Pickpockets!’ only for the officer to respond with a shrug.

A video posted to Diego’s Instagram feed, meanwhile, shows him filming a woman trying to steal a purse from a shopper in M&S on Oxford Street at 7pm in late July. He calls the police to inform them that the pickpocket has been apprehended by store staff, only to be told, ‘I’m sorry, we don’t have any units available’.

My second lesson is that confronting criminals, even in broad daylight, is not for the faint-hearted. At several points, the man Diego pursues across Green Park seems on the verge of attacking him. Earlier this week, two pickpockets he spray-painted chased him carrying wooden sticks and glass bottles.

Diego enjoys ju-jitsu as a hobby, but he has also developed a healthy instinct for self-preservation. A couple of other recent near misses have persuaded him to invest in a stab-proof vest.

His famous red paint is also a sort of safety product. Marketed as a ‘criminal identifier’, it comes in a pocket-sized can and is often sold as an accompaniment to a rape alarm. Diego doesn’t spray it on every ‘picky-pocket’, instead limiting its use to when he’s attacked, or on ‘repeat offenders’ who he’s caught more than once.

‘I started using it this summer because I was seeing pickpockets, and shouting at them, but they would cross the street and walk away and then just carry on stealing,’ he explains.

Guy Adams joined Diego at Buckingham Palace amid the throng of tourists who had gathered to watch Changing of the Guard

‘The paint is a way of marking them. It doesn’t wash off so when I paint someone they have to go home and give up for the day.’

Diego’s moral code is probably rooted in his childhood. The son of a police officer from Curitiba, a city in southern Brazil, he reckons a talent for spotting thieves (or ‘rats’) is in his genes.

He ‘fell in love’ with London in 2017, after his employer, a firm that provides forestry equipment, sent him to the UK to complete an English course. And thanks to his Italian passport (like many Brazilians, he boasts European heritage), he was able to move here two years later. Today, he lives in a shared flat near the Thames, and earns £150 to £200 a day doing bicycle deliveries for fast-food apps including Deliveroo, Uber Eats and Just Eat.

Diego cottoned on to the scourge of pickpockets in 2023, while waiting to collect a delivery outside a restaurant in Soho, when he saw a suspicious man walking out with a handbag that didn’t belong to him. Diego gave chase and retrieved it. After that, he started ‘seeing things happening all the time’. But despite reporting several incidents – some he even had footage of courtesy of the GoPro he’d attached to his bicycle helmet in case he was involved in a traffic accident – the police never bothered to investigate.

‘In the beginning, I was calling 999, saying a pickpocket has just stolen from someone and I have tracked them. They would ask: ‘Do you have the victim?’ and I’d say: ‘No, the victim won’t be there, I’ve followed the criminal,’ and they’d say: ‘In that case, we can’t come.’ I’ve gone up to policemen and pointed out pickpockets to them, but they refuse to stop and search them because they say they aren’t allowed,’ he says. ‘In the end, I gave up and thought that if the police won’t do anything, I can.’

His first social media clip, depicting a gang of Romany gypsies targeting tourists on The Mall, was uploaded on July 12, and quickly attracted several thousand views and scores of admiring comments.

In the weeks and months that followed, he developed a network of informants, including between 20 and 30 delivery drivers, who message him whenever they spot a suspected crook, along with ticket-sellers working for open-top bus companies, whose customers are targeted as they wait at bus stops.

On the two or three days each week he devotes to catching pickpockets, he can usually hook one in a couple of hours. On some occasions Diego has followed his targets discretely, gaining an intimate understanding of the gangs behind the ongoing crimewave.

While there are several groups from Chile and Peru (he can recognise their regional accents), the vast majority, he says, hail from Romania or Bulgaria. They come to London for months at a time, before moving on to other European tourist destinations. Several individuals he’s filmed have popped up on videos shot by other social media activists in Paris or Milan.

Often, they target elderly tourists with expensive-looking handbags, or anyone wearing a rucksack on their back in a crowd. Chinese visitors are particularly vulnerable, because they are used to city centres filled with facial recognition cameras and authoritarian soldiers and police officers, so pickpocketing is an alien concept.

On the day I join Diego, the thieves melt away to other tourist hotspots once Changing of the Guard has finished. At lunchtime, his phone pings with images of a prolific group (including several ‘familiar faces’) working the streets outside the Tower of London, but instead we head to the Houses of Parliament, scene of some of Diego’s most memorable videos.

He nudges me. On the pavement, two young women are walking behind a Chinese tourist. One has placed her hand in the woman’s Burberry rucksack. The other is using a shawl to conceal her accomplice. Up goes the cry: ‘PICKY-POCKETS!’

We follow the duo through Westminster, with Diego bellowing warnings. We catch up with them in a back street, where the women (at least one of whom is pregnant) light up cigarettes, and ask what might persuade their Brazilian tormentor to leave them alone.

The women say they are Romany gypsies from Bulgaria who are stealing to feed their families. Diego agrees to let the duo wander off, provided they agree not to return. ‘If I see you again, you’re getting painted,’ he declares.

‘Of course, I don’t believe they will give up pickpocketing,’ he says. ‘Pickpockets have no shame.’

But for this afternoon, at least, the streets of central London will be that little bit safer.