So I picked up the box and took a look, and the use-by date was 2007. While I suspect that it is probably still OK to eat, I also suspect that any nutritional value is now gone, and what's left is a sort of dry fossil. Might also be some weevils in there, I didn't check. Maybe appropriate for vampires (Spike liked his with blood), but probably not entirely fit for human consumption.
Really must try to remember to buy some cereals...