An A-level exam paper stolen and sold for £400 a copy before the exam had been sat has sparked a police enquiry.

The illicit paper may have been changing hands all over west London after it was revealed that a copy of Pure Maths Paper 2 was discovered in Ruislip before being handed over to the authorities.

A Metropolitan Police spokesman said: "We can confirm that we are investigating whether exam papers have been stolen or compromised in the west London area."

The news of potential cheating has angered many students and teachers in Hillingdon because others may have gained an unfair advantage prior to the examination on Thursday last week.

Hillingdon Association of Head Teachers (HASH) spokesman Rod Stafford said: "Pupils walking into the examination after hearing this news have acted with bewilderment and anger. They are outraged if other students are gaining an unfair advantage through sheer dishonesty."

Asked whether he thought the source of the alleged leak may have come from a Hillingdon school, he said: "It would be very difficult to believe that it started from Hillingdon. I am confident that schools in the rest of the borough have similar procedures to my own school, Mellow Lane, where exam papers are couriered in directly to the headteacher and then kept in a safe before being taken out on the day of the exam."

The exam board, Edexcel, has said that anyone it suspects of having obtained the paper before the exam will have their results cancelled.

A spokesman for the board said: "We have two years worth of estimated results for all candidates so far. We are pretty confident that we can catch any cheats."

With police still trying to establish whether a crime has taken place, Mr Stafford believes that Edexcel must take legal action against alleged cheats to ensure the protection of the exam system.

He said: "Very severe and exemplary proceedings should occur if there has been cheating. The integrity of any examination should be absolute."

By.Michael Lau