It had been a wet November. Rivers and streams were swollen with run off from the hills. Penda’s army was wet, miserable and, for reasons that are not entirely clear, disgruntled.

Unlike his elder brother, Oswiu received no saintly dream visitor telling him to attack, even though he had given oath to give his daughter, Ælfflæd, to the church and to found many monasteries should he win victory. So it was most likely his perception of a sudden tactical advantage that decided Oswiu to attack.

When report came back from his scouts that Penda’s army was struggling to cross a swollen river, with some of the army on the far bank and the rest stuck on the near bank, Oswiu saw his opportunity.