there's no need to be so picky about the question and poll. look, you clearly know what he's asking, and so does he. So if your interested, answer the question, if your not, don't.
As for me, i only did history until GCSE and even then we only did super modern stuff or ancient. So i don't know much between ancient and modern.
On my basis of limited knowledge, i would have to agree that the battle of the Somme was the most devastating defeat, but not the most important one. I think the most important one was the Norman conquest. If it wasn't for that invasion, i don't think Britain would have began to progress as quickly or as far. the Norman touch brought a little flair to Britain, and thank you for it.