Leeds Grammar School sixthformer Nadav Winehouse stepped out of an A/S exam and was stunned to find Deputy Prime Minister Nick Clegg waiting for him.

Nadav, who is studying politics, had tweeted an invitation to Mr Clegg to visit the school but had assumed nothing would come of it.

Unknown to him, the Liberal Democrat leader’s aides had contacted the school and unsuspecting students were summoned on the pretext of a revision session.

Mr Clegg, in Leeds on the final day of election campaigning, held a Q and A with them.

“When he arrived I couldn’t believe it was happening”, said the sixthformer. “I was expecting someone from the exam board.”