Nine members of one of the country's largest ever cannabis growing rings were beginning jail sentences totalling almost 30 years on Thursday July 23 2009.

The illicit skunk cannabis - with a street value of at least £21.2 million - was commercially cultivated in at least 33 rented houses, 11 of them in Southport and Formby, which appeared externally to be respectable homes.

But when police raided the properties, located mainly on Merseyside and Greater Manchester, 29 of them were found to have cannabis growing in them and the others had had or where about to, said Nigel Power, prosecuting.

"The scale and value of the estimated cannabis yield from the conspiracy is startling," Judge David Harris, QC.

"The conspiracy involved the production on a huge scale of skunk cannabis. It was grown in sophisticated and highly efficient artificial conditions designed to ensure the maximum yield of the drug at optimum potency.

"The conspiracy was implemented through the leasing of apparently innocuous domestic properties which were then extensively adapted for the cultivation of cannabis."

Judge Harris said that a total of 33 properties were involved as cannabis factories during the two year four month duration of the plot, the largest ever uncovered on Merseyside.

Liverpool Crown Court heard that when the conspiracy ended on September 17 last year when some gang members were seen entering and leaving properties in Liverpool Road and Marina Road, Formby.

When five of them were arrested a total of eight kilos of cannabis worth £80,000 was seized.

The gang had illegally tapped into electricity from the mains to keep the sophisticated hydroponics systems – with timed heat lamps and feeders – running 24 hours a day.

The property landlords were left with huge repair bills averaging £20,000 following the secret factory adaptations, said Mr Power.

The eight Chinese men and one woman, all but one illegal immigrants, admitted or were convicted of conspiring to supply cannabis. The sentences they received ranged from six years four months to 14 months.

The tenth gang member before the court, Nicole Parker, 20, of King Street, Newton-le-Willows, who had been recruited by Li, received a 12 month suspended sentence, was ordered to carry out 200 hours unpaid work and placed under a curfew for six months.