But there is only one person I blame for getting shafted, and that's myself. I went into the deal which I thought would secure the future of Orange Aids with culpable impetuosity. I had been used to doing business on a handshake and my work of honour, and I made the error of actually believing what the men in the pin-striped suits told me.

I'd work eighteen-hour stretches and fall asleep in my clothes. Then I'd wake up in the middle of the night, brew a pot of tea, and start work again. I was tired, but work had become pure enjoyment.

Ideas for gadgets for the disabled were coming into my head so fast they seemed to be arriving from somewhere outside of me, beamed down by an unremitting force. I had little control over them, or their flow. I would wake up in the middle of the night. A blinding flash of an idea would rouse me from my bed and I'd rush down to my workshop to have a go at it before the inspiration dimmed.

A good idea turns every cog in your mind, making you scared of bed in case the whole machine grinds to a halt.

But having had your bright, fresh, original idea, the really hard part is turning it into a successful product. That's what takes all the sweat.

Invention isn't some impenetrable brand of magic; anyone can have a go.

That was the Alka-Seltzer moment, the moment when the tablet hits the water and begins to fizz.