He's designed bald patch detectors, giant chairs, shoes that let you walk on water, flying machines, and amphibious cars.
But Keith Alexander is best known for his invention of the Springfree trampoline. Reputedly the world's safest, more than half a million have sold worldwide.
But success comes with the ever-present threat of rip-off merchants copying his designs, and sometimes strained relations with the investors backing his ideas.
