A gang who farmed millions of pounds of cannabis in one of Britain's biggest dope production conspiracies was jailed for a total of 90 years today.

Motivated by "financial greed", the group produced "industrial quantities" of the drug in the garden of England between 2013 and 2015.

A total of seven factories were discovered at industrial sites in Gravesend, Rochester, Sittingbourne, all Kent, and one at North Walsham in Norfolk.

A total of 16,428 cannabis plants were seized from all the sites, with an estimated street value for a single year of between £25,418,160 to £51,852,840.

The huge operation came to light after police uncovered a cannabis factory in Rochester in June 2013, following reports of a burglary.

Officers entered and found the factory inside the industrial unit, which had been leased by James Allen since December 2012.

Police found Allen, along with others, had rented three industrial units in the Canal Basin in Gravesend, using false details.

The seizure from that farm alone represented "the largest cannabis production seizure in the United Kingdom at that time", the judge noted.

A total of 15 people, aged 18 to 69, admitted their roles in the conspiracy, or were convicted.

Sentencing 14 members, who were crammed into the dock at the Old Bailey, Judge Anuja Dhir QC said: "You were all involved in a highly professional, well-planned, organised cannabis production enterprise.

"Between 2013 and 2015 the industrial sites - six in Kent, one in Norfolk - were rented by you to turn into cannabis factories.

"Five of them were in active production at the time of the police searches.

"Those five were expertly adapted and skilfully equipped to enable the production of vast industrial quantities of cannabis.

"Considerable planning went into disguising the operation, and who was involved. Some of you were more involved then others.

"But you were all involved, aware of the professionalism and the scale of the criminal agreements you were involved in."

She added: "You were wholesalers. But ultimately those drugs were going to be sold on the streets of this country.

"The estimated annual street value of the cannabis produced in one year was over £50 million.

"Each of you was motivated by financial greed.

"I am satisfied that the separate premises can, individually, properly be described as an operation capable of producing industrial quantities for commercial use."

Mastermind Michael Edward Corcoran, 51, of Yalding, was convicted of seven counts of conspiring to produce cannabis and five counts of abstracting electricity, and was jailed for 14 years.

The judge told him: "You were the head of this crime group. You were the mastermind of it, and had overall control.

"You involved your family, your friends, your business associates."

David Graham, 50, of Bromley, south east London, admitted five counts of conspiring to produce cannabis and five counts of abstracting electricity, and was jailed for nine-and-a-half years.

Judge Dhir said: "You played a leading role in this criminal enterprise."

James Allen, 39, of Abbey Wood, London, admitted five counts of conspiring to produce cannabis and three counts of abstracting electricity, and was jailed for seven years.

Stephen Macey, 25, of Paddock Wood, admitted five counts of conspiring to produce cannabis and five counts of abstracting electricity, and got six years' jail.

Christopher Marsh, 30, of Margate, Kent, admitted one count of conspiring to produce cannabis and one count of abstracting electricity, and was jailed for four years.

Damon Mills, 18, of Margate, pleaded guilty to one count of conspiring to produce cannabis and one count of abstracting electricity, and got 18 months in prison.

Michael Jay Corcoran, 28, of Gillingham, Kent, was found guilty of four counts of conspiring to produce cannabis and four counts of abstracting electricity, and was jailed for eight years.

Stefan-Alex Henderson Clarke, 27, of Walworth, south east London, was convicted of four counts of conspiring to produce cannabis and four counts of abstracting electricity and was given a seven-and-a-half years' sentence.

Stuart Sollis, 51, of Camberwell, south east London, was found guilty of five counts of conspiring to produce cannabis and four counts of abstracting electricity, and was locked up for eight years.

David Heath, 48, of Peckham, south east London, was found guilty of three counts of conspiring to produce cannabis and three counts of abstracting electricity, and was jailed for seven years.

Asked if he understood before he left the dock, he yelled: "No I don't. Who the f**k is Michael Corcoran? I don't even know him."

Colin Walls, 52, of no fixed abode, admitted one count of conspiring to produce cannabis and was convicted of two counts of conspiring to produce cannabis and three counts of abstracting electricity, and was jailed for six years.

"You were the head of this crime group. You were the mastermind of it, and had overall control" - Judge Dhir

He was linked to a factory by DNA on a cigarette butt.

Terrance Murphy, 47, of Purfleet, Essex, was found guilty of one count of conspiring to produce cannabis and one count of abstracting electricity, and was locked up for three years.

Stephen Creed, 45, of Great Yarmouth, Norfolk, was convicted of one count of conspiring to produce cannabis and one count of abstracting electricity, and received a six year sentence.

Andrew Prowse, 32, of Camberwell, south east London, admitted three counts of conspiring to produce cannabis and got two-and-a-half years in prison.

Alan Marquiss, 69, of Thamesmead, south east London, admitted one count of conspiring to produce cannabis and one count of abstracting electricity, but will be sentenced at a later date.