Three men have admitted running a large cannabis factory in a former nuclear bunker in Wiltshire.
More then 4,000 cannabis plants – enough to produce £2m of drugs each year – were seized in a raid on RGHQ Chilmark in February.
Martin Fillery, 45, Plamen Nguyen, 27, and Ross Winter, 30, pleaded guilty at Salisbury Crown Court to conspiracy to produce class B drugs and abstracting electricity.
They will be be sentenced on 11 August.
The former Ministry of Defence bunker was built in the 1980s to protect local dignitaries and government officials in the event of a nuclear attack.
Following a midnight raid Wiltshire Police made their biggest ever cannabis factory discovery.
Det Insp Simon Pope said: “The bunker itself had approximately 20 rooms inside over two floors, and almost every single room had been converted for the wholesale production of cannabis.
“In addition to the growing rooms, there were drying rooms, nurseries and living quarters for the growers – it was a sophisticated set up.
“In all it took approximately 10 days to completely search and clear the site.”
Police said the gang had illegally abstracted approximately £250,000 worth of electricity for a setup “capable of producing a crop every six weeks”.
Fillery, of Pedwell Hill, Ashcott, Bridgwater; Nguyen, of Bartholomews Square, Horfield, Bristol; and Ross Winter, of Maytree Avenue, Bristol, also faced charges of conspiring to hold another person in slavery/servitude.
But Wiltshire Police said these charges had been dropped due to a lack of evidence.