I start doing serious research to see of this idea has legs, frantically checking whether anyone has ever invented a backpack like the P3. Amazingly, it seems there is nothing like it out there. I start intensive work on prototype development in my workshop: the living room. With no garden shed or garage, I have to spread tools and materials all over the carpet, hoping I don't injure anyone. The P4 prototype is a step backwards, but the P5 makes some huge strides forward. Although long ago, my Engineering degree from Cambridge University finally proves incredibly useful in visualising solutions and building working models. Things are really taking shape.