It's a Mystery was a networked Children's ITV programme which ran for five series from 1996 - 2002. It was produced by The Media Merchants Television Company Ltd and Meridian Broadcasting Ltd. Series five was simply called Mystery.
It was a programme that educated children by challenging them to solve a mystery. Usually this would involve people telling stories of mysterious occurrences that have happened to them, such as a Man in a Van driving up to a roundabout and seeing his exact duplicate across the roundabout, driving the same vehicle.
Other times, the presenter would show unexplained phenomena such as ghosts in the Tower of London or the Loch Ness Monster. The presenter would then offer up possible explanations as to what might have been behind the mystery or if there is even an explanation to give. After each story, it would be given a solved or unsolved designation. At the end of each episode, a riddle would be asked for the audience to solve until the next episode (where the answer would be given).