Most of the Ordinary Meetings of the Institute provide an opportunity for specialists to report on work that has been carried out, or experience that has been gained. From time to time, however, we have a meeting designed specifically for the purpose of discussion. The main aim of such meetings is to enable interested persons, with quite different backgrounds of knowledge and experience, to come together and consider collectively a subject of common interest from their various viewpoints. The present discussion is on the significance of gross human errors and blunders in navigation.