Guardian: When I decided to give up shopping for a year, it was all about the grand environmental gesture. I’d already made a start. I gave up eating fish six years ago, and then flying four years later, and I wanted to stretch my commitment a little further, to see if I could do without something that I’ve always enjoyed. Or at least assumed I had. I didn’t give much thought to what it would involve at first; I just wanted to lighten the load of those vast, smoke-belching cargo ships by a few …