Police probing an international smuggling ring found more than three tonnes of drugs when they raided a garage.
Detectives discovered 180 boxes of cannabis resin in the garage in Wakefield, West Yorks, and another 120 in a nearby van.
The stash weighed 2,996kg and was worth £12.9million.
Nearly 270kg of herbal cannabis valued at £1.1million and 89kg of superstrong skunk cannabis at £750,000 were also recovered along with £170,000 in cash.
The haul was damning evidence against a gang which imported drugs from north Africa via Holland.
Det Insp Stuart Spencer said: Removing this network undoubtedly had an impact upon the availability of drugs, minimising the misery they bring to communities.
Andrew Lee, 46, of Wakefield, his brother Graham, 43, Robert Price, 55, and Scott Weaver, 29, all of Leeds, admitted drugs charges and will be sentenced at Leeds crown court.
By Jon Clements