A former scaffolder explains why he would never go back to his old job after turning to cannabis production for "easy money".
Sky News was invited into one large-scale operation somewhere in south London where we met two British workers who dedicate their lives to this illegal horticulture.
Wearing a decorator's mask, track suit top and shorts, one worker gave us a guided tour, explaining how their operation works.
There are around 30 cannabis plants potted in tubs in one small room that is rigged up with several hot lights, there's gardening equipment in the hallway along with tens of thousands of pounds worth of the class B drug.
The worker said: "I have been working here four years - I used to be a scaffolder.
"Obviously scaffolding is good money but I wanted a bit more money and a better life, so I got involved and started learning a new trade."
After years of growing them and caring for them the worker said: "They are like humans - they get ill, you have to use chemicals - you have to treat them when they get ill ... you have got to handle them like you do your own kids.
"It is a full-time job. When people say it is easy - it may be easy selling it, but is not easy growing it. It takes all my time up."
The illicit factory is within a property adjoining another legitimate business.
The worker admitted: "I'm on a really big scale of it, you know, there is even more stuff that you haven't seen.
"We have got places which are full up with stuff ... the money is excellent, really good.
The gang revealed how they also operate a franchise system, preying on people who are ready to hire out a spare bedroom.
The worker said: "What it is is people on benefits and that and they are struggling and we give 'em a bit of money to use two rooms or whatever we want.
"For one room we will give 'em £200 or £300 a month ... if it ever got caught by the police it is not in our name it is in their name and that's, that's what we do."
The worker has seen how UK-produced cannabis has come to dominate the market for a drug that was once predominantly imported from abroad.
He said: "It is that big they will never be able to control it - it is on a massive big scale what everyone is doing, it is not just us.
"The new trade now is people doing this instead of going to work ... it is hard work but it is easy money - right at the end of it is a nice payout."
He then grabs a nearby black holdall and showed us the stash of cannabis, bagged up and ready to be sold on the street.
"These are ounces, they go for £250 - I do 'em at £200 - but if you broke them down into little bits into £20 shots you could earn about twenty grand from all this - maybe more."
He had few qualms about this strong version of cannabis ending up in very young hands.
"Yeah young kids - I know 12, 13-year-olds smoking it, even 11-year-olds ... it mellows them out, makes you in a good mood and it is a nice little buzz."
Before he returned to tending to his plants I asked if he would ever return to scaffolding, the worker simply replied: "Never ... never."
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