It's a classic flying flashpoint and one that brings out all manner of human vulgarities. Is it really the height of bad manners to recline your seat without ask the passenger behind if they mind? Really?
And if your request is met with a, "Well, actually, I'm quite tall and I'd prefer if you didn't", what then?
Is that it? No room for compromise? Do you have to negotiate a personal-space treaty? Work out a roster system? Or is it just, London, here we come...bolt upright.