Watching the Arsenal match in a local pub today, and noticed that every single guy who walked in was greeted with the news that Man United lost today - smiles, laughs, sometimes even whoops for joy.

Can someone explain to me why exactly Londoners (or, it may just be people in general, you tell me), HATE them so much? I'm pretty sure that most of these guys weren't actually Arsenal supporters, because they weren't watching the match, and I'm aware that they're old rivals - so - what's the deal here?