We describe our routine identification of images of asteroids and comets on plates and films in the U.K. Schmidt Telescope archive. The asteroids of most interest to us are those which approach the Earth, and whenever such an object is found (by anyone) we perform backintegrations in order to determine whether the object may have been recorded on any UKST plate taken since 1973. In many cases the object is found (‘precovered’) and measured, allowing an accurate orbit to be determined soon after its discovery; other studies such as long-term dynamical investigations, or predictions of future close approaches to the Earth, are then possible. Similar programs using other wide-field plate archives are to be encouraged, since valuable scientific results may be derived.