But despite this alleged incident, the normal procedures for "live" examination papers are very strict.

Examination papers are sent to school in sealed, tamper-proof envelopes in good time for the examination date.

The papers come in secure packs

Teachers can check they have the right number of papers by means of a special window on the envelope.

They can also check they have the correct papers because each has a special code which can be checked through the window.

"All the details can be checked without the envelope being opened," said George Turnbull, spokesman for the Joint Council for General Qualifications.

"So then the envelope is opened in the exam hall in the presence of the students - there is no need to open the package before it gets to the exam hall."

Locked storage

Before a school or college can become an exam centre the exam boards demand they have certain facilities, such as a hall where the desks can be arranged at a certain distance apart.

Each centre must have a locked, secure cabinet or store to which only certain members of staff have access.

If there is anything suspicious, we will pay particular attention to that centre

George Turnbull, Joint Council for General Qualifications

Exam boards inspect centres regularly throughout the year to check everything is in order - and some of those inspections are unannounced.

"We've always been aware of the need to keep centres under review to see exams are being administered to a satisfactory standard," said Mr Turnbull.

"And if there is anything suspicious, we will pay particular attention to that centre.

"Security is of paramount importance in exams."

Mr Turnbull also stressed that students should not be put off by stories which appear in the media.

"They should try and forget what they read or hear of and concentrate on their own exam and do the best they can.

"Examination boards bend over backwards to ensure students are not disadvantaged in any way by a situation beyond their control," he said.