When history begins, fEthelberht, king of Kent, was supreme over all the kings south of the Humber.
In support of this explanation it is urged that the title is given in the Chronicle to Ecgbert in the year in which he "conquered the kingdom of the Mercians and all that was south of the Humber."
The Levels, as this district is generally named, are of remarkable fertility, and Thorne, having water communication with Goole and the Humber, is consequently an agricultural centre of importance; while some barge-building and a trade in peat fibre are also carried on.
Another theory is that Bretwalda refers to a war-leadership, or imperium, over the English south of the Humber, and has nothing to do with Britons or Britannia.
The best notion of the process of warping may be gained by sailing up the Trent from the Humber to Gainsborough.