A Vietnamese man has been jailed at Shrewsbury Crown Court for running a country-wide force of illegal immigrants to grow huge quantities of 'skunk' cannabis.
Toi Van Le's (51) empire included four 'factories' in Stoke-on-Trent and a processing unit in Burton upon Trent.
When police raided a house in Hillary Street, Stoke, they discovered a sophisticated set-up with 240 plants under cultivation.
Altogether there were 800 plants growing in the four homes he had converted into cannabis factories across the city.
At a house, in Uttoxeter Road, there was a total of 300 plants spread across three rooms and the cellar. Cut plants were found stored in the lounge.
In a property in Cauldon Road, police found three first floor rooms equipped with extractor fans, ducting pipes and plant growth liquid in the bath.
Police forces across the country were involved in rooting out his operations in other areas.
Van Le was arrested by West Midlands Police and convicted on nine charges of conspiring to produce cannabis.
After a 17-day trial, his business, said to have been worth millions of pounds, cost him 11 years and ten months in prison.
He was sentenced on December 21.
He had earlier admitted one charge of conspiring to produce cannabis at a terraced house in Chilton Street, Stoke.
Cannabis - growing success
Inspector Mark Churton, of Staffordshire Police, said: "We are having more and more success in discovering production facilities and closing them down."
He said the police were eager to speak to anyone with information about cannabis production and possible drug misuse.
People can get in touch by ringing '101'.
They can also give information anonymously via Crimestoppers, on 0800 555 111, or by using their online form by clicking here.