A gigantic cannabis factory hidden by secret lifts and false walls has been described as Britain’s ‘most sophisticated’ weed farm.

Police discovered 20 hidden rooms inside the former mill, containing 1,300 cannabis plants valued at about £760,000.

But the stash was completely hidden from plain sight – with a lift providing access to upper floors of the building disguised behind a stone fire place.

It was found by police officers who smashed their way through breeze block walls inside the building in Darwen, Lancashire.

A 31-year-old man was arrested inside the mill, which had specially built living quarters designed for long-term use, police said.

Detective inspector Vinny De Curtis said: ‘Almost every single room had been converted for the wholesale production of cannabis plants.

‘This was an enormous set-up – I am convinced it is one of the most sophisticated set-ups in the UK.’

About 16kg of cannabis buds, valued at £230,000, were inside, along with £250,000 of production equipment including lamps.

It is believed the building was used by organised crime gangs to create industrial amounts of cannabis.

DI De Curtis added: ‘This is the largest and most sophisticated cannabis factory I’ve ever experienced and I am delighted that we have been able to take such a large amount of illicit drugs off the streets of Lancashire before they are able to reach vulnerable people within our communities.’