Signed for is not tracked. You can check if it has been delivered, but if it goes missing there is no way of knowing where it is. Unfortunatly all sorts of things can and do happen to letters, sometimes the flap isn't stuck down properly, the corner gets caught in a sorting machine and the whole letter gets shredded. Sometimes it gets caught up with another letter (can happen if there's a bit of loose sellotape). All sorts of stuff. If something is very important than you can send it special delivery, which is tracked the whole way and doesn't go through the sorting machines, it's all sorted in a special, locked office. But that service does cost a minimum of £6.22. I know that we shouldn't have to pay that sort of money to guarantee that post will get there, but unfortunately accidents do happen.