Nik talks a lot of sense about technical interviews. As a purely anecdotal aside, I'm pretty sure that the interviews where I've been asked the kinds of questions that he's talking about have lead to some of the jobs that I have least enjoyed.
And, as Nik mentions, this is all in the context of Guardian Unlimited looking for a lot of new employees (I can't help wondering how permanent that URL is). Having worked at GU a couple of times, I'd recommend working there to anyone. It's certainly one of the best places I've ever worked.
"I can't help wondering how permanent that URL is"
Actually, you'd be surprised. When we went to drop the content in at that URL we were surprised to find there was already a page there, some long-forgotten recruitment blurb from about six years ago. So perhaps the /joinus URL will last slightly longer than you (or I) would expect.