Nuff said I think. Now, the back of the Express Post envelope says "If we do not deliver as promised, you will receive another C5 Express Post envelope free". Wicked man, wicked.
In all honesty, this sort of thing (having an express post not arrive the next day) hasn't happened to many people at all - it's certainly the first time it's ever happened to me. That's why I firmly believe that someone is using voodoo powers against me.