He is the supply teacher at Launceston College in Cornwall who subjected himself to national humiliation by appearing on a recent edition of the ITV talent search programme The X Factor.

The 44-year-old, who was genuinely convinced of his own star potential, told judges he wanted to achieve “multi-platinum-selling albums all over the world”. He sang a version of Spandau Ballet’s “Gold”, which ended on a sustained . and then sustained . and even more sustained note. “Get me through, and I’ll make sure they’re longer,” said Mr Blackwell.

“You can’t make them any longer than that,” said judge Simon Cowell.

Mr Cowell appeared equally unimpressed by the teacher’s rendition of “Your Song”, which ended on another sustained note. The judge pointed out that with songs on the liveshow stretching to just one and a half minutes, Mr Blackwell’s performances would have to consist of a single note, and no song. He was duly voted off, despite Louis Walsh, former Boyzone manager, in favour of sending the supply teacher into the next round.

Mr Blackwell’s pupils have since posted excited comments about his performance on YouTube. One said: “omg he’s a supply teacher from mi school omg hes soo cool but his singin isnt.”

Another suggested: “when he calls your name in the register, answer, `Here siiiiiiiiiiiiiirrrrrrrrrrrr.’”