"Hello," says Billy Baxter to the hall full of nine and 10-year-olds sitting in front of him. He pauses for a comic moment, then gives a cheery grin. "Woz my problem, then?" He is, he tells them, blind. "And today I want to take you into my world. I can't see anything. That's why I have these black glasses and a white cane. Close your eyes. That is what I see when I wake up, and when I go to sleep. It doesn't matter if my eyes are open or shut."
The 41-year-old former staff sergeant went blind while serving in Bosnia, from a bacterial infection that damaged his optic nerves. "But only four out of 100 blind people will be totally blind like me," he tells the children, then gets them to make "binoculars" with their hands, so they can only look forward - "that's tunnel vision", and to make fists in front of their eyes, so they can only see a little bit around the edges - "that's central vision loss." They hang onto every word. He's a natural performer, and ably helped by "the lovely Rebecca", who hands around glasses for them to look through to get an impression of what it's like to have cataracts, or glaucoma.
Billy "The Whizz" Baxter is the heroic holder of the blind motorcycle world speed record since 2003, and clearly someone who isn't going to let the little matter of being blind spoil his appetite for life. "Blind people can do all the things you guys can," he tells them. "Drive anything, ride anything. Provided they've got someone else's sight to help them."
The hour-long presentation is part of a programme of citizenship education devised by St Dunstan's, the charity that supports blind ex-service men and women. It uses St Dunstaners to contribute their experiences to help children learn more about the consequences of conflict and disability, and offers a history presentation based on the experience of one of the first St Dunstaners in the First World War, for key stage 3 children, as well as this KS2 citizenship presentation, "A World Without Vision". Piloted in 150 schools, it is now going national, with the aim of reaching 384 schools a term within five years. Additional units and resources are also planned.
Billy has been doing it for four years and has made about 250 visits. "It's fantastic," he says, as he meets the attentive children at St Mary's Roman Catholic Primary School in Eltham, south London. He explains how people without sight have to rely on other senses, such as touch, for everyday tasks, like getting dressed - "That's got arms, that's a jumper" - and tells them a story about how he once went out wearing his wife's nightie instead of a T-shirt. Colour can be a problem. "I could end up with bright orange trousers, one green shoe and one blue one, and a bright purple tie."
Then he shows how he puts knots in his ties, so he knows which is which, and a high-tech pocket gadget which speaks the colour of anything it scans.
There's also a gadget that can tell you what's in tins, he says. "Otherwise you might end up eating a tin of sausages when what you were wanting was rice pudding for your afters."
He also tells them how to offer help to a blind person - not by grabbing their arm and marching them across the street, but by saying, "Hello, I'm so-and-so. Do you need any help? How can I help you?" Give them your elbow, he says, and act as their eyes, warning them about kerbs and obstacles. And just say hello, he suggests, to be friendly, even if you're not offering help. "Sometimes when I'm out with my white cane I feel as if I'm on another planet."
A chaotic scene ensues, with Megan being a lamppost and Lucy a mad driver, while Billy is guided by Zachery around multiple obstacles.
Then the questions flood out: how does he watch TV? Does he dream in colour? Some questions, he says later, are too close for comfort. "Some of them are belters. 'Do you miss seeing smiles,' was one. I could feel myself welling up, so I quickly said: 'Yes. But I make up for it with kisses and cuddles'."
Anna Robinson, of St Dunstan's, says teachers often can't believe how well-behaved children are for these presentations. "At one school the teacher said they would have to sit on one pupil to keep him quiet, but he sat with his hand up, all the way through."
The programme has lottery funding and is supported by the DfES and the Ministry of Defence, but more funds are needed to reach the 2010 targets.
However, there is no shortage of schools wanting to invite the charity in to pass on its message, and many have now hosted two or three visits.
"You are young citizens," Billy tells St Mary's pupils. "You are tomorrow's future. Make sure you help each other out when you've got problems, and try and make your environment a better place."
* St Dunstan's Schools Education Programme:www.st-dunstans.org.uk