A former mill with secret lifts and false walls has been busted and named as one of Britain's most sophisticated drug dens.
The property in Darwen, Lancashire, was discovered to house 1,300 cannabis plants valued at around £760,000.
Police also found around 16kg of cannabis 'buds' worth £230,000, as well as production equipment valued at £250,000.
With 20 hidden rooms, a lift disguised as a fireplace, and breeze block walls, it's no surprise that it went untouched by police for some time.
Officers made the discovery when smashing through the lightweight walls.
The criminal operation was so secretive that the mill even had a specially designed living quarters for long-term use.
Lancashire Police confirmed a 31-year-old man was arrested at the scene.
Detective inspector Vinny De Curtis said of the haul: "There were approximately 20 rooms in the building, split over three floors.
"Almost every single room had been converted for the wholesale production of cannabis plants.
"This was an enormous set-up - I am convinced it is one of the most sophisticated set-ups in the UK.
"The actions of officers yesterday took a large amount of planning and teamwork, and I am very pleased that it has been so successful."
Using a Misuse of Drugs Act Warrant under Operation Mercury, police were able to bust into the mill, with the help of Lancashire Fire and Rescue as well as the UK Border Agency.
The building is believed to have been used by organised crime gangs to create industrial amounts of cannabis.
Several police units, including CSI vans, operations support units, unmarked cars, and police dogs were seen outside the mill for several hours.
The debate over making cannabis legal in the UK will, of course, rage on.
Dr Henry Fisher, policy director from drug policy think tank Volteface, previously told LADbible that the current legislation for cannabis doesn't work.
He said: "We're left in this interesting situation, and there's no other policy or criminal sense quite like it, where what the reality is and what the rhetoric is, is so different.
"If you read any drug related story in which there's a statement from the Home Office it says the same thing 'drugs are illegal and are bad for people in communities' and that's why they're illegal.
"If you legally regulate it and control it you can have a wider choice of products, you can create tax incentives so that maybe products that are stronger or more dangerous are more highly taxed so that there's an incentive for people to buy safer forms of cannabis."