Three men employed as gardeners at a large-scale cannabis farm, which could potentially produce almost £4m worth of the drug a year, were put behind bars today.

Liverpool Crown Court heard that police uncovered the sophisticated drugs operation on a Birkenhead industrial estate after using heat seeking equipment on a force helicopter.

They kept the Marshall Street unit under observation for nearly three months and secretly watched as brothers Karl and John Faulkner and friend Michael Cree ran the operation.

Geoffrey Lowe, prosecuting, said when officers eventually decided to arrest the men on October 12 last year as they drove away in a van, Cree made a desperate attempt to escape.

He smashed into a police car before mounting the pavement, hitting an officer and a tree, then colliding with another car. Fortunately the officer was not seriously injured.

When police entered the industrial unit they discovered more than 1,550 plants at various stages of growth.

The factory had been divided into a “nursery” for the youngest plants and a “growing room” full of flowering female flowers.

Mr Lowe said that the estimated value of the plants uncovered was up to £616,000.

But he said that over the course of the year, with a harvest every three weeks, the factory could have produced cannabis worth £3,687,640 over a year.

Cree, 26, of Treborth Road, Blacon, John Faulkner, also 26, of Fford Cae Llwyn, Connahs Quay and Karl Faulkner, 36, of Elm Road, Ashton Park, Deeside, all pleaded guilty to producing cannabis. Cree also admitted dangerous driving.

Gerald Pachter, defending, said that Cree only has one old conviction and works as a self-employed builder.

Although his partner asked him to move out because of the stress of the situation, he is still a "very good father" to his two young children.

"His involvement started in a bizarre way to look after his family financially because of the slump," said Mr Pachter.

He added that he was a gardener and had not been involved in setting up the operation, management or distribution.

He should have been paid £3,000 but only received half that sum.

Mr Pachter said that Cree had not deliberately driven at the police but had just panicked and driven recklessly.

Defence barrister Simon Driver said Karl Faulkner had taken a gamble last summer by getting involved but quickly regretted it and wished to extricate himself.

He is a family man who has been working part time and this will be his first taste of custody, he added.

Jonathan Duffy, defending John Faulkner, said, "He is a joiner by profession. But he found himself in increasing financial difficulties and was offered an opportunity for a modest amount of money."

Faulkner was paid £200 a time but quickly "came to his senses" and realised the impact of what he was doing but was unable to extricate himself.

He has two young daughters and a partner.

"He understands more than anybody the very serious jeopardy he has put that in by his crazy decision to get involved," added Mr Duffy.

The judge, Recorder Nicholas Fewtrell, said, "This was a large scale, sophisticated cannabis factory."

He told the trio that he accepted that they were "gardeners" but pointed out that they were "important cogs in what was a very significant operation."

Jailing each of them for two years for the cannabis offence, he said he would be failing in his public duty if he did not send them into custody.

He also sentenced Cree to six months' imprisonment to run consecutively for dangerous driving and banned him from driving for two years.

After sentence had been passed, Detective Superintendent Lee Halstead from Titan, the North West Regional Task Force, said in a press statement: "These three men were involved in the significant production of cannabis, which was bound for the streets of the Northwest and potentially beyond.

"Officers from Titan worked alongside our partners in Cheshire, Merseyside and North Wales to investigate these offenders and ultimately take them off our streets.

"Drugs and their associated criminal activity is a blight on the lives of innocent residents and will not be tolerated by police forces across the region.

"Titan is committed to tackling serious organised crime across the North West.

"Working together with our partners across the regional forces and local communities, we are determined to disrupt and ultimately halt the activity of those prepared to engage in this sort of crime."