A police officer who discovered a loophole in Tesco’s Clubcard loyalty scheme has been convicted of cheating his way to 18,000 Air Miles.

PC Shaun Pennicott faces losing his job after being convicted of “going equipped to cheat” when he repeatedly abused the supermarket’s self-service checkouts.

In two months the loyalty points he collected would have paid for six return flights between London and New York.

Tesco admitted yesterday that the loophole was still open. It would cost too much to close it but procedures were in place to alert the company if any of the 13 million families that use its loyalty scheme attempted to abuse it.

Pennicott, 42, had become obsessed with collecting loyalty points, visiting his local Tesco “morning, noon and night”, Luton Crown Court was told.

The father-of-two had discovered that coupons for loyalty points could be used repeatedly because there was no barcode reader in the slot for the coupons on the self-service checkout machines.

Samantha Leigh, for the prosecution, said that Pennicott would sometimes use the same voucher three or four times. Each bonus point is worth a penny and every £2.50 Clubcard voucher can be converted to 60 BA miles.

“We say he was obsessed with Clubcard points,” she said.

Pennicott discovered the loophole when a supervisor helped him to use the self-service checkouts when they were installed at the Tesco Extra branch in Watford town centre in November 2005.

In the two months between December 2005 and January of last year he made 154 transactions at the store. On every occasion he used the 150 bonus points coupon, collecting a total of 75,000 loyalty points on his two Clubcard accounts which were automatically converted into British Airways Air Miles.

On one occasion he went into the store and bought a newspaper, taking it to a self-service till to pay. He then scanned the barcode of a coupon promising an extra 150 loyalty points three times, clocking up 450 points.

Ms Leigh told the court that in September 2005 the officer had legally taken advantage of a Tesco promotion involving Bird’s Eye meals. In three days he bought 759 of the cheapest meals and received 38,000 Clubcard points.

Tesco called the police when the officer’s Clubcard accounts were flagged up by the store’s computer to be security checked because of the number of points.

Kay Clements, the operations manager for Tesco, told the court: “We knew about the situation at the trials stage . . . we have calculated the loss and it is not enough to warrant the investment of putting a reader in every machine.”

Pennicott, a constable with Hertfordshire Constabulary for 14 years, was was found guilty on Friday of eight charges of going equipped to cheat. He was fined £800 and ordered to do 120 hours’ community service.

Pennicott, who has a holiday home in Tenerife, told the court that he planned to high-light the loophole and his transactions were to be examples he could show to the company.

“As long as I tell Tesco of this problem then surely I am not committing any offence,” he said.

Judge Michael Kay told him: “This became an obsession in my judgment. You were so greedy you would do virtually anything to obtain Clubcard points and turn them into Air Miles. You regularly travelled abroad and that is what attracted you.” The judge described his defence as “preposterous”.

Chief Superintendent Jeremy Alford, of Hertfordshire Constabulary, said after the case: “I expect police officers to be honest and act with integrity. Shaun Pennicott did not live up to the standards I expect.”

Pennicott is expected to resign from the police, his barrister said, or face disciplinary proceedings with the likelihood that he would be dismissed.

A Tesco spokesman said yesterday: “In terms of the number of people who do this there may be one here or there.

“But there are ways of being able to tell who is abusing the system.”

Self-service checkouts were first introduced in Britain in the early 1990s and reintroduced in the late 1990s. There are now an estimated 500 machines in use at stores including Tesco, Marks & Spencer and Asda.

How he cheated

— How the Clubcard scam worked, as described to the jury at Luton Crown Court:

— PC Shaun Pennicott obtained a Clubcard from his local Tesco

— He was sent a coupon by the supermarket offering him an extra 150 loyalty points

— The officer attached the barcode from the coupon to the back of his Clubcard keyring fob

— At the supermarket’s self-service checkout he scanned the barcodes on the Clubcard and coupon

— When the checkout machine requested the coupon, he inserted a blank piece of paper and then withdrew it. There is no barcode reader in the machine to check if coupons are genuine

— His Clubcard account was credited with the extra points

— Pennicott repeated the scam up to four times on each shopping trip

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