Nearly half a million GCSE papers are being recalled from schools after a batch was stolen at knifepoint from a delivery van.

The Assessment and Qualifications Alliance and the Oxford, Cambridge and RSA exam boards decided to replace the English language, drama, German and Persian GCSE papers on Wednesday.

The papers, which also included English literature, geography, and Spanish GCSEs, turned up in a Croydon street on Friday - a month after they were stolen in nearby Mitcham. The boxes were bound for three schools in the Croydon area.

An AQA spokeswoman said: “The boxes were found by members of the public and some of the papers were missing. We have decided to replace the papers because of this.”

Some of the OCR papers which were stolen were taken by pupils this week. An OCR spokesman said: “Because of the complexities caused for teachers awarding bodies do not automatically replace papers.”

AQA will replace 430,000 English language higher and foundation papers, due to be taken on June 10 and 14 and 33,000 drama writing exams, due to be taken on June 18. OCR are replacing 4,000 German papers and 500 Persian papers.

At Strode’s college in Surrey, caretakers interrupted an AS-level exam to get extra chairs for a reception which the Duke of Edinburgh was attending to celebrate the sixth-form college’s 300th anniversary.

Principal Frank Botham said that the school tried to make it as normal a day as possible, but that four students were disturbed during their exam due to a misunderstanding between a junior member of the caretaking team and a temporary member of staff. The students were given extra time.

A palace spokesman said: “When the Duke of Edinburgh visits a school he always insists that it should in no way interrupt the day-to-day running of the school. This will have been a matter for the school. It has not come from the palace.”