I am not sure I have the emotional fortitude to get into this. What is the definition of a 'proper chicken'? And if they don't exhibit all the characteristics of a proper chicken (which I might imagine include things like predator awareness, raising young, foraging) does that mean it is OK to lock them up in awful conditions?
Even if they are 'less than' chickens in the eyes of whoever decides these things I still think they deserve to be treated with respect and given the chance to lead a full life to their ability.
But I am fully aware I am a hypocrite because I don't feel the same about the bugs I feed my own chickens.
Anyone who wants to really bend their mind around this question would do well to read
Never Let Me Go by Kazuo Ishiguro (incidentally a British author). It is a novel and not about chickens but speaks directly to the question Shad asked and is a very good read.
Shutting up now.