Well, I'm still working on my idea but I'm willing to share it with you.
I'm working on an invisibility device that can turn me invisible when I enter the machine in my laboratory. It works and I can turn invisible for hours on end. Great you might think, but it's nothing of the sort.
My plan was to walk into The Bank Of England and walk out again with as much money as I could. Then I realised I'd be caught because they could see the money moving through the air and hold on to it.
So it was back to the drawing board. Now I'm working on an invisible sack to put the money in!