How about: The sun's burning down. You sit behind a table in the market, your guide dog at your feet, lapping up water from its bowl. You're selling cool drin

How about: The sun's burning down. You sit behind a table in the market, your guide dog at your feet, lapping up water from its bowl. You're selling cool drinks of lemonade to passers by. You have a glass on the edge of the table, above your dog. For £1, you let customers pour lemonade into the glass and take a drink. Then along comes Mrs Peabody, who hates your dog. She pays you £1 and pours lemonade into your cup. But she keeps on pouring. Because you're blind, you don't see the cup overflowing and the lemonade pouring into your dog's bowl. After Mrs Peabody goes away, the dog laps up the lemonade and feels sick. You don't know why. If only you could see enough to make people put the right amount of lemonade in the glass, you'd have been fine.