Betfair self-matching on horse racing?
I think that someone self matches on the horse racing and I would guess it is Betfair itself. It takes very little for your order to move the market, yet the market matches 1000 - 3000 pound order routinely. Someone will buy a 2000+ then sell 2000+ 200 milliseconds later or vice-versa. That would cost a lot to do if you weren't self matching. So either someone has a very sophisticated algorithm or more likely, someone is self-matching.