As an assistant chief examiner, Mr Gleave still moderates AS and A-level art in a number of schools.

The optimum number of six school visits per examiner, agreed with the exam board two years ago, has now shot up to 10 because of the shortage of examiners. He said: “With 10 schools it is going to be a struggle this year, there is even talk of 12 centres. One new moderator took one look and said ‘I’m not doing that.’ ”

With staff shortages and supply cover practically impossible to find, headteachers are reluctant to let teachers out for examiner training, despite the pound;120 they receive from the exam boards to cover costs. Art moderating is even more time-consuming. Each session can take about three hours out of the day.

Mr Gleave, who teaches at Kendrick school for girls, in Reading, said:

“Some visits can take more time because the school’s marks are not accurate. I might not get home till 10pm sometimes.

“Art supply teachers are practically impossible to get. I’ve only come across one since I’ve been teaching. And other staff say ‘I can’t cover art, I don’t know anything about it’.”

On the plus side, examiners find out what is going on long before everyone else does.

“When I started teaching, the school art department consisted of me and a part-time art teacher. Examining was a way to keep in touch. It was a case of how can I get more free training?”

The money was not the motivating factor. Moderators get about pound;40 to pound;50 per school on average.

Mr Gleave said: “We are not paid properly. Art people have to travel. My car gets hammered in June and July - I get 32p a mile.”

Mr Gleave believes the Government needs to step in.

“I’ve had four examiners threaten to drop out this year. If they go, I’m going because I’m not going to take up the slack. Art moderators are at the sharp end. It is not just sitting in your house marking scripts. We are dealing with people and emotions.”