More than 700 people have been arrested in Britain and tens of millions of pounds have been seized after the police infiltrated a top secret communications system used by criminal gangs.
It’s being called the biggest and most significant law-enforcement operation ever carried out in the UK.
The gangs were using a device that looks like a normal mobile phone. But each one costs up to £3,000 and they were used by high-level criminals to talk to each other.
The gangs believed nobody could listen in, but they were wrong.
Sophie Raworth presents BBC News at Ten reporting by Home Affairs correspondent Tom Symonds.