Cannabis worth more than £1m was uncovered at a Wirral industrial estate after police saw a motorist acting suspiciously.

Liverpool Crown Court heard that fortuitously police had gone to the Old Brickworks site in Carr Lane, Moreton, because the alarm on a car outside the perimeter fence was sounding.

While checking it out they saw a Vauxhall Astra inside the site and on spotting them the driver, Paul Fletcher, seemed to panic and reversed away, said Michael Stephenson, prosecuting.

"They stopped the vehicle and discovered it had been loaded with cardboard boxes containing a very substantial quantity of female flowering cannabis heads."

Mr Stephenson said that they weighed 28 kilos and an expert calculated it had a street value of £520,000.

A police sniffer dog brought to the site was attracted to a sealed container and, after officers got two brothers working at a metal working business on the site to burn it open, a further 30 kilos of cannabis was found in similar cardboard boxes.

The total value of the drugs, believed to have come from about 1,200 plants or successive flowerings from fewer plants, was in excess of £1m.

"It was obviously a large scale professional operation to accumulate that quantity," he said.

Judge Mark Brown said that the cannabis must have been cultivated at different houses in Wirral, picked up and taken to the site for onward delivery.

The court heard that 36-year-old Fletcher had initially claimed that he had been an "unwitting dupe" but now accepted he was to be paid £250 to act as a delivery driver.

Fletcher, of Berrylands Road, Moreton, who trembled uncontrollably throughout the hearing, was jailed for two-and-a-half years. He admitted possessing cannabis with intent to supply on May 5.

"Your role was a delivery man, in the sense you were recruited to act as a courier. You accept it was a trusted role and were fully briefed," said Judge Brown.

"You also accept it involved a significant amount of cannabis. You went into this enterprise with your eyes entirely open.

"It is apparent that the site was being used as a collection point for the drugs which had been cultivated at different locations on the Wirral and delivered to this site and from there were to be delivered for onward supply."

The judge added that Fletcher, whom he described as "well-spoken of and a good father," was a difficult individual to assess.

"You present as extremely nervous and I am conscious prison will have a significant impact on you."

His barrister, Philip Astbury, described Fletcher, who has no previous drugs convictions, as living an itinerant lifestyle.

He had never held down a job but did not claim benefits and had difficulty in keeping meaningful relationships.

"But he has a decent, warm and loving side to him. He suffers from depression and has a history of self-harm and has found these proceedings very difficult.

"He accepts he was a courier and knew what he was collecting but did not know what was in the container," added Mr Astbury.