An off-duty police officer stumbled across two secret rooms hidden behind a mirror in a Great Yarmouth flat that were being used to grow dozens of cannabis plants, a court heard.

Sergio Paula and Rui Siopa pleaded guilty at Norwich Crown Court to growing 25 large cannabis plants yesterday, but claimed that they were for personal use only.

Malcolm Robins, prosecuting, told the court that they had been caught earlier this year when an officer noticed a 'strong smell of cannabis in the air' as he walked past the building they lived in.

Officers got a warrant to search a garage on York Road on May 7, but when they got inside they realised the smell was coming from the flat above.

They knocked on the door and Paula, 26, gave them permission to search inside the house.

They found a small, two-bedroom flat, but behind a mirror in one of the rooms was a hidden door leading to two secret areas where 25 cannabis plants were being grown. High-powered lights had been installed in the rooms, as well as an extraction fan to remove the pungent smell of the plants.

Police arrested Paula and took him to Great Yarmouth police station, and Siopa, 28, returned to the flat before the last officers left and was also arrested. Police estimated that the mature female plants could have yielded as much as �40,000 worth of herbal 'skunk-type' cannabis each year, by producing three crops.

Mr Robins said that in December 2007 the electricity bill for the property 'started to go through the roof' from �70 to �200. Paula pleaded guilty to producing cannabis, but said that he was not paid for his work and only helped out by occasionally watering the plants.

Danielle O'Donavan, defending Paula, said: 'What he was doing was growing so he could get a bit for himself.'

Kevin Batch, defending Siopa, said that he had also grown the plants only for his own use and that it was not his intent to sell any.

Recorder Mark Evans adjourned the case until November 11 at Norwich Crown Court.

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