Simon Armitage: 'And the further I climb the more adamant it gets in its opposition, as if a whole North Atlantic weather front has come bursting through the collapsed dam of Bellcrag Flow, pouring through the gap, so that any progress is progress upstream, against the flood, into the rapids, with boulders and logs of hard air piling into me and knocking me sideways. It should be torture, but it's exhilarating, ecstatic, a frenzied initiation or hysterical reacquaintance with the great outdoors. And I think: this is why I came, to stumble into the unexpected, to feel the world in its raw state. I open my mouth to shout "MORE", but the force of air just rams the word back into my mouth and down my throat.'