In a nuclear bunker build in the 1980s to house VIPs in the event of a nuclear attack, thousands of cannabis plant worth more than 1 million pound was found during a raid of the site.
Aged between 15 and 45, six men have been arrested following the raid on RGHQ Chilmark in Wiltshire.
Following a tip-off, Wiltshire police officers raided the site, which is disused but still intact with its nuclear blast doors in place.
“We found this huge operation inside”, said Detective Inspector Paul Franklin.
“There are approximately 20 rooms in the building, split over two floors, each 200ft long and 70 ft wide,” he said.
“Almost every single room had been converted for the wholesale production of cannabis plants, and there was a large amount of evidence of previous crops. This was an enormous set-up.
“It is almost impossible to work out how many plants are inside, but we are talking thousands rather than hundreds and we would estimate the value of the crop at over £1 million.”
On Wednesday, the police officers waited outside for people to leave the bunker at night.
Three men, from Somerset, were arrested as they were leaving the building. Their keys were used to enter the building.
Three more men, believed to gardeners were arrested from inside the bunker.
The men in the bunker were arrested on the suspicion of cannabis production and those were outside were arrested on the suspicion of cannabis production and human trafficking offences.
It is not the first from large quantities of cannabis production found in unusual places.
Last year, police found at least 1,000 cannabis plants at a luxury nine-bedroom country mansion in March, Cambridgeshire.