The dogs don't pull in front as they are attached to the bike by a thing called a Springer. It's a special metal attachment for bikes and dogs. We found the Springer at Crufts a few years ago and the dogs just love it. When Benji sees his harness he goes nuts coz he knows he's going out on the bike.
So I suppose this answers everyones questions. Douglas doesn't fall off as he's not holding on to the dogs. They don't pull in front of the bike or go under or into the wheels. Douglas also said that he starts the dogs off very gently at a walking pace with the bike and then gradually builds up speed. The dogs take to it extremely quickly.
Sorry, I prob should have explained about the Springer beforehand. :o