Chocolate slot machine

It is rare that my brother is able to dredge up embarrassing memories from my past of which I have no recollection whatsoever. Last night, over whisky, he told me of an occasion over Christmas about thirty years ago when we had both been given one of those chocolate selection packs: Bounty bars, Milky Ways and so on. At the time, he was very keen on the concept of the slot machine - pressing buttons, pulling levers and so on. With a degree of cunning that I find it hard to imagine I possessed at the age of nine, I persuaded him to join in a game in which I had invented a chocolate slot machine. I think it was made out of a duvet. All he had to do was press imaginary buttons and in return he would receive a bar of chocolate. The only payment was that the slot machine's controller would take an initial bite out of the bar of chocolate in question. What William failed to recognise at the time was that this was HIS selection pack of chocolate and I was therefore appropriating my brother's rightful property...