'Crikey!' Boris wrestles with whiteboard as stand-in teacher

It was a lesson with a difference for sixth-formers at the St Marylebone Church of England High School first thing yesterday morning. After all, stand-in teachers are not supposed to show their glee at the prospect of the Prime Minister being arrested over the "cash for honours" affair. Nor, for that matter, do they often admit that "the trouble with politicians is they're incredibly vain". And nor are latecomers often greeted in such hail-fellow-well-met fashion: "Are you going to join the class? Brilliant!"

But in this case, the supply teacher for the lesson at the London comprehensive was Boris Johnson - the Conservatives' higher education spokesman and sometime television celebrity.

He was part of a week-long celebration of the Teach First initiative - under which graduates who have not trained as teachers are given the chance to work in the classroom on leaving university. A dozen celebrities - including the Newsnight presenter Jeremy Paxman - have signed up.

Mr Johnson began by telling his audience he was a Tory MP and to take into account that - at times - he might seem "unnecessarily prejudiced". He admitted to being a little nervous - "although perhaps not nervous enough" - before entering the classroom. He has taught English and Latin before, in Australia, but that was before the introduction of the interactive whiteboard which proved just a little bit too interactive for him. The trouble was that it changed slides at the merest touch - unlike the old blackboard - and so a presentation of different options for reforming the House of Lords suddenly disappeared. "Oh crikey!" he cried, with a Bunteresque wail. "How do I make that reappear? We never had these when I was teaching."

Technical support soon resurrected the lesson and the pupils were then told of the four options for reforming the House of Lords - replacing it with an elected second chamber, an appointed second chamber, a mixture of the two or keeping the status quo (with 92 hereditary peers). "How many peers are there in the House of Lords?" Mr Johnson asked his class before admitting: "We don't quite know because they keep dying all the time." They settled on somewhere between 741 and 752.

He told them that Jack Straw - "You've heard of him? It isn't a disgrace not to know Jack Straw" - who was drawing up proposals for the Government, wanted a mixture of an elected and appointed second chamber. He said the main plus point with the present system was that "they [the peers] do it for free". "They turn up, OK they get their expenses and some then knock off but a lot of them really are superb guys speaking against legislation for the good of the country."

The biggest minus point - both for the present system and an appointed house - was the possibility of corruption, he said.

At the end of the lesson, he asked his class of 21 - 19 girls and two boys (the school is girls' only except for the sixth form) - to vote on the four alternatives. Most favoured Mr Straw's proposal. "This really is a Straw poll," said Mr Johnson.

He said afterwards he had found it "shattering" to be on his feet for 55 minutes delivering the lesson. "It is a very hard job although it can be incredibly rewarding," he said. "I do see what people can get from it." He had, though, no plans to adopt it as an alternative career in the event of an exit from the political arena.

The pupils said their new teacher had been fun. Florence Bridge, 16, said: "It was good. I liked it, although he is quite biased." Helen Bailey, 17, added: "He's got quite a lot of charisma. I didn't agree with some of the things he said, though."