Police have seized more than 1,700 cannabis plants which had been grown in a March mansion.
Officers shut down the cannabis factory at the £1 million Wendreda House, off Saxon way and Wimblington Road, on Wednesday.
The haul, with an estimated street value of £300,000, is one of the largest discovered in a Fenland residential property in recent years.
Det Insp Dave Murphy said: “We have seen that volume in an industrial unit on an industrial estate but never, in recent memory, had so many plants in a fairly posh mansion.
“It was a professional job. The contrast – downstairs is almost like a stately home, then you walk upstairs and every room is full of plants.”
Officers discovered the cannabis factory after receiving a tip-off from a concerned member of the public. Five detectives went to investigate and discovered the haul. Officers spent more than three days clearing out the mansion of the plants.
Two men, a 33-year-old from Whitstable, in Kent, and a 30-year-old man from Twickenham, West London, were arrested on suspicion of producing cannabis.
They have been released on police bail and will report back next month.