I used to bet on the national every year in much the same way Steve. I had similar doubts but actually stopped a few years back when working for William Hill. The amount of effort put into it by the bookies is unbelievable. The build up lasts for weeks and every employee has to work that day. When you see the amount of money they make on that single meeting, you can see why!

Incidentally I made about £200 on a little experiment a couple of months back. Using a Web sites free trial I got free bets from most major bookies and laid those bets off on another site. It was eye opening that most of the money was made laying off rather than betting.