Pearson Edexcel says marking has now resumed and there has been no impact on its ‘accuracy or integrity’, after issues emerged last night.

Students sitting maths exam today only discovered the problem once papers had been opened – now AQA promises to contact schools before results day to ‘explain what we’ve done to make sure no learners are disadvantaged’.

Around 23,000 people have signed a petition calling for ‘unusally difficult’ exam to be reviewed, but Pearson Edexcel says the paper was ‘rigorously checked’.

England’s exams regulator, Ofqual, is "closely monitoring" the marking of an A-level maths paper after a petition demanding a review garnered over 15,000 signatures in less than 24 hours.