Andrew Ritchie, inventor of the Brompton folding bicycle, once said that the perfect portable bike would be“like a magic carpet. . . You could fold it up and put it into your pocket or handbag”. Then he paused:¡¡“But you’ll always be limited by the size of the wheels. And so far no one has invented a folding wheel. “

It was a rare—indeed unique—occasion when I was able to put Ritchie right. A 19th-century inventor, William Henry James Grout, did in fact design a folding wheel. His bike, predictably named the Grout Portable, had a frame that split into two and a larger wheel that could be separated into four pieces. All the bits fitted into Grout’s Wonderful Bag, a leather case.