Undercover police officers posed as drug users during a three-month operation to infiltrate Didcot's heroin scene.

The officers, known as 'Gaz', 'Matt' and 'Kelly', went into the town to gather evidence on dealers during Operation Meerkat, Oxford Crown Court heard yesterday.

Simon Mayo, prosecuting, outlined the case against 11 people arrested during the investigation.

They include Nathan Greenwood, 31, and 23-year-old Steven McDowell, both of Westfield, Harwell, near Didcot, who were found guilty of conspiracy to supply class A drugs.

Also to be sentenced for conspiracy to supply heroin are Darren Presley, 32, of Druids Walk; Steven Presley, 29, of Mendip Heights; Aaron Hoey, 26, of Wessex Road; Nicholas Alner, 44, of Nuffield Close; Cathie Ward, 27, of Mendip Heights, all of Didcot, and Lindsey Fowles, 21, of Elderfield Crescent, Chilton.

Ricky Kilroy, 23, of Nuffield Close; John Fenn, 24, of Sinodun Road; and Karl Bergan, 34, of Venners Water, all of Didcot, will be sentenced for supplying drugs.

Mr Mayo said: "The police acted as drug users from out of town, getting in with local users and convincing them they were in need of heroin.

"Contact was made with Hoey and Ward and they were introduced to Steven Presley and McDowell."

He said Darren Presley was a wholesaler of heroin, who got his brother Steven to sell drugs on the street.

Presley moved into a flat with Fowles, but police had fitted a covert listening device there and later raided it.

Mr Mayo said: "Fowles was Darren Presley's partner, who assisted him by packaging the drugs and monitoring them when they were passed on to his brother." He said on June 26 last year, Hoey offered to help the undercover officers buy heroin.

He said: "They were waiting for Steven Presley, but Hoey said since they had a car, they could meet 'Stevie', that is Steve McDowell.

"McDowell gave Hoey three foil wraps of heroin."

"On June 30, Hoey approached McDowell again to enquire if he could supply drugs and they arranged to meet in a car park behind the Co-op store in Didcot.

"Mr Presley arrived and they had a short conversation, during which he supplied 'Matt' with heroin."

On another day the officers offered Steven Presley £500 to go to London to buy half an ounce of heroin -- an offer he accepted.

The operation ended in early August and the defendants were all due to be sentenced today.