Kjartan Poskitt wears blue jeans, a black and yellow rugby shirt, and a Rupert Bear scarf. Fashionable sideburns adorn his cheeks and he sports a queen of hearts tattoo on his left arm symbolising his love for “Mrs Poskitt and the four little girl Poskitts”. He’s not how you imagine a maths guru. But then, as 10-year-old Anthony Clark says, he’s really a “mathemagican”. He’s also “hilarious”, “silly”, “creative” and “kind” say Anthony’s classmates at Brunshaw Primary School in Burnley, Lancashire.

The former stand-up comic and author of Scholastic’s successful Murderous Maths series has just delivered a riveting performance on strange number facts, flexagons and magic squares. Polished tricks, silly jokes and cheeky questions rendered in chummy Yorkshire jabber enthral the 250 children at Brunshaw. The teachers are laughing out loud, too. Maths has never been so much fun.

Kjartan needs a volunteer. A hundred little hands shoot up, but this time he chooses a teacher. Mr Taylor is instructed to write down secretly a three-digit number (724). Write the same number backwards (427), says Kjartan, and then subtract the smaller number from the bigger number.

“Can you see the numbers?” he asks the teacher sitting next to him.

“No.”

“She’s been looking at me. Who can blame ‘er! Has the new number got a 9 in the middle?” he asks Mr Taylor.

“Yes.”

“What’s the first digit on the last line?

“Two.”

“Is the number 297?”

“Yes.”

There’s a curious number fact. If you reverse a 3-digit number and subtract the smaller from larger, the middle number on the last line is always nine, and the first and last digits always add up to nine.

Another trick: if you multiply 1089 by nine, you get 9801 - the number has turned itself round. And the winner of the most useless piece of information in maths on Kjartan’s website is the number “forty”, because it is the only number with all its letters in alphabetical order.

“Who thinks that’s really, really sad,” asks Kjartan, pulling a face as he winds up his audience into fits of laughter.

Questioned later on his favourite maths fact, he confides it is that if you put 32 dominoes on a chess board (each domino covering two squares) there are 12,988,816 ways of arranging them (yes, we know there are only 28 dominoes in a set, but that’s not the point).

But the funniest bit is to come. Kjartan does magic as well as maths. He pulls out two model shapes made of folding paper - his hexaflexagon and pentaflexagon. “These scruffy bits of cardboard are probably my most favourite things in the entire world,” he says.

On the hexagon is a man’s face. The man owns a dog. Kjartan concertinas the hexaflexagon - in and out - and the face disappears. He pretends to be the dog and whimpers for his master. Another deft squeeze or two and the face reappears. Happy dog. Next time the face appears in mismatched pieces and the dog is distraught.

“You’ve bin listening? Good on yer. Give yerself a round of applause.”

Next he makes a pentagon and, after more tricks and laughter, holds it up to the children: “Who wants it?” Another 100 hands shoot up. “I’ll give it to this fella down ‘ere. ‘Ere you are, boss.”

It’s a rollercoaster of maths merriment or, as assistant headteacher Catherine Greenwood put it, “an excellent example of how we endeavour to make learning fun, real and challenging for the children”.

When the pantomime is over, a group of Brunshaw’s more able children ask Kjartan whether he was in the top class for maths at school.

“Yes, I was in the top maths set at school,” says the engineering graduate and former Rosie and Jim author (who, incidentally, has not an ounce of Icelandic blood in him, despite his first name). “I can’t kick a football to save my life, but I’ve always been fortunate that I can chuck numbers round in me ‘ead.”

In 2003, Brunshaw was 6 per cent short of meeting its school target of 24 per cent for maths level 5. It decided to target improvement strategies at more able pupils by setting problem-solving activities, and at professional development, and this year achieved its 26 per cent target. Brunshaw, described by Ofsted in 2001 as a “very effective school” with “excellent leadership,” has a below average socio-economic background with 32 per cent of its children receiving free school meals and 29 per cent with special educational needs.

Kjartan Poskitt’s relationship with the school has been made possible by Brighton Festival’s Adopt an Author project, which targeted Birmingham, Belfast, Cambridge, Swansea, Brighton and East Lancashire, thanks to Pounds 60,000 from the National Endowment for Science Technology and the Arts. In East Lancashire alone, six professional writers - Julia Donaldson, Jean Sprackland, Berlie Doherty, John Foster, Malorie Blackman and Kjartan Poskitt - have been corresponding by email with chosen schools. The correspondence with 18 bright Year 6 children has had a major impact on Brunshaw’s improvement strategies. And for Kjartan himself, replies to his email teasers have not only provided impetus for his writing, but sometimes amazed him at how quickly the children have solved them.

Try this one: “You go to shop and buy something for pound;1.12 and you pay with a pound;5 note. The shopkeeper gives you change using the smallest possible number of coins. When you look at the collection of coins you’ve got, there’s something curious about it. What is it?” Kjartan says some adults would have difficulty with this puzzle, but the Brunshaw children solved it straight away. The answer is: one of each of the different denominations of coins are in the collection.

The quirky number show is no snip at pound;600 a time, but Kjartan is so popular, he could book himself a gig for every day of the year. Now then, tha’ tells yer summat ‘bout numbers, dun’t it?

* www.kjartan.co.uk