So do I, of course remembering that this is a completely fictionalised version of events.

There's no reason to believe that Æthelflæd was captured by vikings and impregnated by Erik Thurgilson before marrying Æthelred. Or that Æthelred was any more a misogynist than any other 10 century christian king. However, we can be pretty sure that Uhtred the bold wasn't even born at this point, never mind Æthelflæd's lover.