When four Hertfordshire boys set off into the Snowdonia hills last Easter on their Duke of Edinburgh Gold Award Expedition the weather was fine and their spirits high. By nightfall misfortune had overtaken them and there began a series of events which led to four days and nights of lonely fear and discomfort for the boys and to the biggest search operation ever mounted in that area. With the help of the four boys and many of those who took part in their rescue, tonight's film recreates the events of that weekend and looks at some of the lessons which can be learnt from them. This, on the eve of the boys' return to Snowdonia to complete their expedition and hopefully to gain their Gold Award. Reporter VINCENT KANE Producers JOHN HEFIN EVANS and GERAINT STANLEY JONES