Fond as my memories of Rosemary Sutcliffe are, if you want to get a grip on the historical 'Arthur' and the period of the invasions may I suggest John Morris' The Age of Arthur. Cedric was a common enough early English name so there is absolutely no reason to equate one fictional Cedric with another or with any real Cedric.
The historical Arthur probably fought a number of battles against the various Germanic invaders but he certainly didn't fight at Maldon. The battle of Maldon, as celebrated in a famous epic poem, took place in 990 CE between English forces under the command of Earl Brithnoth and Viking Raiders. As Maldon is on the coast of Essex it would be a highly unlikely place to find Arthur in any event.
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The historical Arthur probably fought a number of battles against the various Germanic invaders but he certainly didn't fight at Maldon. The battle of Maldon, as celebrated in a famous epic poem, took place in 990 CE between English forces under the command of Earl Brithnoth and Viking Raiders. As Maldon is on the coast of Essex it would be a highly unlikely place to find Arthur in any event.