I've just been reading a biography of James IV, and it claims the battle of Flodden happened essentially by accident.
The Scots took up the position which had Surrey attacked head-on, the English would have got destroyed. Surrey, realising this took his army on the march on the evening of the 8th. This was spotted by the Scots who believed the English Army was retiring to a nearby village and thus never changed their position for the battle and the rest is history.
Now, what if the Scottish Council of War on the evening of the 8th had realised that the English Army was changing position and withdrew from the field back to Norham. With Henrys northern-most fortress in Scottish hands and a huge army on the border, how do you think this would have affected the war?