A suspected gang of Romanian and Lithuanian pickpockets is about to get an early-morning wake-up call as a sleepy street in Barking, east London, is invaded by armed police.
As the police march in single file, the sound of their heavy boots echoes around the estate, stirring residents out of their beds to peep through their curtains.
On cue, a group of officers shout: "Police! Police!" as they slam a heavy metal rod into the front door of a terraced home. They break it open and a dozen officers swarm inside.
The front door of a neighbouring house is also smashed open, and there are screams and shouts from terrified occupants who are hustled into the living room while the houses are searched for stolen goods.
Scotland Yard says it has received intelligence that organised gangs from South America and Eastern Europe are planning a crime blitz during the Olympic Games.
These dawn raids may seem heavy-handed, but police say such gangs pose one of the biggest criminal threats to the Games.
"Operations like this are a pre-emptive strike to put pickpockets out of business before a surge in tourists in the capital," Det Insp Mark Teodorini explains.
"We know where people are. We know the addresses they are using, we know the vehicles they are using, and we will come through their door very robustly - and if we find anything on them, we will arrest them."
In an internet cafe in Barcelona, 900 miles away, one of those gangs says it is preparing its Olympic operation.
Johnny, Mario and Danny - as they referred to themselves - are part of a network of 50 Romanian pickpockets operating in the Spanish city.
They say they are now aiming for gold at the London Games.
The petty thieves struggle to hide their excitement as they conduct their research on the internet, scanning through images of bustling shopping centres near the Olympic Village and overcrowded tubes and buses.
They even plan their escape routes using satellite images of the streets of east London.
Danny has been a pickpocket since he was seven.
"It's in the blood, it's all I know. This is what we do and we do it well," he says, handing back the wallet I thought was still in my back pocket.
'Magic to distract'
It took little persuasion to get the gang to talk after we were introduced by a cafe owner; they appear to be proud of the skills they say were taught by their parents.
Johnny pulls out a pack of cards and makes them disappear under his arm.
"Look, I do magic to distract the tourist and woo - their wallet or phone is gone! It takes just one second and their vacation is ruined."
They tell me that they have strict rules to escape detection and arrest: No drinking, so they keep focused; and no mugging, to avoid a scene.
"Some of the pickpockets are hooked on drugs or they spend all their money in the casino and they get desperate, they are violent. We are not like them," says Johnny.
"Cameras, laptops and phones are sent back to Romania to be sold on the black market and we can make 5,000 euros in a week because a tourist left his bag a second, you know, a second."
When asked if he and the others feel guilty, Johnny hesitates and eventually whispers: "Yeah, I do".
To get a closer look at their "one-second theft", I offer to become their victim. They demonstrate a tactic named after Ronaldinho, the footballer who dances when he scores.
Johnny approaches with a map, asking for directions, while Mario and Danny pretend to be drunk, swinging their arms and forcing me to dance.
They run off in different directions and Danny returns, proudly holding my wallet. I didn't notice a thing, it all happened so quickly.
"I am the distracter," explains Johnny.
"Mario is the pickpocket or the distracter because he is very experienced, and if he takes your wallet or phone he hands it to Danny; he is the runner.
"That way the tourist has no idea who did it or who has their belongings."
'We are too quick'
On the beach and in the surrounding bars, the panic of tourists desperately searching for their phones and wallets is an obvious sign pickpockets are about. But only a trained eye has any chance of spotting one in action.
Johnny agrees to give another insight into his world, pointing out about four teams of pickpockets patrolling the beach looking for targets, like sharks circling their prey.
He knows all the gangs, but warns they will be too quick to stop and some are too dangerous to confront.
Suddenly, one of the groups move in on a young holiday-maker, using the Ronaldinho tactic.
As they walk briskly away, they empty the cash from the tourist's wallet and divide it.
The other groups move in, emptying the pockets of unsuspecting tourists forced to do the silly dance.
"In London, CCTV and the police have to be quick to catch us," Johnny says.
"We will dress and act like tourists to mingle. They will not spot us in crowds of hundreds. We are too quick."
So far, more than 80 suspected pickpockets have been arrested during police operations ahead of the Olympic Games.
The head of Operation Podium - Scotland Yard's team dealing specifically with crime connected to the Olympics - admits public vigilance is needed, along with the 9,000 extra police officers looking for thieves.
"We won't always get them in the act but we are trying to disrupt their activity," Det Insp Mark Teodorini says.
"It is going to be a hostile environment for pickpockets. My advice to them is don't bother."