While the other kingdoms of northern Europe were becoming consolidated under the strong rule of a monarch, it was otherwise with Germany. The Holy Roman Emperor, in theory at least the temporal head of Europe, and still enjoying considerable prestige on that account, was, so far as his actual authority in Germany went, the weakest monarch in Europe. The office was considered too dignified a one to become hereditary, and, like that of the Pope, the spiritual head of Europe, was elective.[32] The electoral privilege was vested in seven Electors; the three Archbishops of Mainz (Mayence), Trier (Trèves), and Köln (Cologne), the Duke of Saxony, the Margrave of Brandenburg, the Count Palatine of the Rhine, and the King of Bohemia. Of these seven Electors all, with the exception of the King of Bohemia, who took no part in the legislative affairs of the Empire, formed the first college of the Diet. Below it stood two other colleges; that of the Princes, spiritual and lay; and that of the Imperial Cities, which had only lately obtained a place. The Diet deliberated on imperial questions, passed laws with the assent of the Emperor, and issued the ban of the Empire against the recalcitrant. But the rivalries between the three colleges, and between the Diet and the Emperor, prevented effective legislation, and it was still more difficult to get laws obeyed, or ban enforced. The Diet was in no real sense a representative assembly. With the exception of the deputies of the Imperial Cities, who were few in number and played an unimportant part, the members sat in their own right,[33] while the lesser nobility, the Imperial Knights, were entirely excluded. This numerous and influential class claimed to hold immediately of the Emperor, and refused to pay the taxes levied by the Diet. Owners, perhaps of one, perhaps of several villages, they entrenched themselves in their strong castles, levied tolls and exercised other rights of petty sovereignty, and, profiting by the old German privilege of private war, disturbed the country with their quarrels and their raids. Nor was the system of imperial justice in any better plight. This lay with the court of the Emperor, called, since 1486, the Imperial Chamber (_Reichskammergericht_). But its jurisdiction was disliked as being too much under the control of the Emperor. The Electors claimed to be free from its jurisdiction, except on appeal for refusal of justice, and in the other states it was impossible to get its verdicts enforced.