In the earlier centuries it was merely a vantage ground.

But when the victorious Romans brought with them the heavy solid fortifications impregnable to the weapons of the time, its commanding position alone ensured its adequate building and equipment.

Then it was that the fortified camp of the Caesars developed into the castle of the king.

As we are as yet ignorant of the names of the first kings of Mercia, no historian has been able to guess which of them made it his ultimate defence; and I suppose we shall never know now.

In process of time, as the arts of war developed, it increased in size and strength, and although recorded details are lacking, the history is written not merely in the stone of its building, but is inferred in the changes of structure.