As a record of past glories, nothing delights the student as much as heraldry. The information that a coat of arms can give the serious scholar is considerable, and over the past 800 years rules have been evolved to control what can be put in one's personal arms and how to show one's descent from other armigerous families. One of the most intriguing rules is that one is not allowed to put metal on metal - gold and silver (Or and Argent in heraldic terms) - or next to each other. Similarly one must not put colour on colour. The reasoning behind these rules has long been suspect, however, so Archbishop Heim's work on the history of, and rules concerning, this subject is most timely. While many authorities maintain that the rules of heraldry forbid such neighbourliness, the author here provides ample evidence that this rule is broken as often as it is adhered to. As a lifelong heraldist and one whose own arms break this 'sacred' rule, Archbishop Heim has always been interested in where and when it was made, so he has researched hundreds of works, some dating from the twelfth century, in an attempt to track down its origins. As a result of his detective work he has painted many examples of arms that break the rule, and also shows how earlier writers have got round such a tricky subject. Or and Argent  contains twenty-four full colour plates containing over 360 coats of arms, with examples from every European country, and many others in black and white in the text, all of which break this so-called immutable rule, and a bibliography giving the most important authorities.