In 1819, made and sold Britain's first bicycle in its hobby-horse form. As a coachmaker Johnson was able to make significant improvements to the two-wheel velocipede, as invented by von Drais. He obtained a patent for his "pedestrian curricle", manufactured them and opened a school teaching people how to ride them. They became a bit of a craze with even the Prince Regent riding them.
Died at home and was buried at St Martin's Chapel, Camden Town.