Round and round the dog track at Walthamstow goes 75-year-old Leo Olley , painting everything that doesn't move. He's there every day before the punters arrive, singing old wartime songs and making sure all is spick and span. "I've got a job for life", he says, "it's just like the Forth Bridge." Greyhound racing is Britain's second most popular sport. It's colourful and exciting and packed with a cross-section of larger than life characters. Johanna Beumer, schoolmistress by day, owner and punter by night, dresses from head to toe in either red, white or blue, depending on the colour her dog is wearing. Tonight it's red. Some you win, some you lose. But as trainer Louis Solomon explains, "If you took away the element of surprise, people would stop coming."