The man, who has not been named, was among seven arrested on suspicion of cultivating the drugs, which were found at a former chicken factory on Barrowhills Lane in Jacksdale.

The Hucknall resident, four Nottingham men aged between 25 and 28, and a 20-year-old foreign national, have been released on police bail pending further inquiries.

Officers found more than 3,000 plants growing in 12 rooms of the factory. Hydroponics and other drug-making paraphernalia, including £250,000 worth of electrical equipment, were disconnected and seized.

The swoop took place after an anonymous tip-off to the free and confidential 'Crimestoppers' hotline.

Chief Insp Mark Wakeland said: "One attending officer, who has executed drugs warrants for the past seven years, said it was the biggest and most sophisticated set-up he had ever seen.

"Cannabis plants were being grown on an industrial scale across the factory floor – a huge space roughly 50m long by 25m wide.

"An immensely professional operation was running on site, to the extent that upstairs office space had been converted into living quarters, complete with a gymnasium.

"We have confiscated approximately 3,000 cannabis plants – an incredible result thanks to information passed on anonymously."

n A 48-YEAR-old foreign national, Thang Nguyen, has been charged with producing cannabis in connection with the raid on the disused factory. He has appeared at Mansfield Magistrates Court.

Nguyen, who is believed to be from Vietnam, did not give a current address.