After Christopher Hitchens wrote a Slate article suggesting that waterboarding wasn't really torture, readers suggested that he try it himself. He did.

So what did it feel like? Hitchens recounts how he was lashed tightly to a sloping board, then, "on top of the hood, three layers of enveloping towel were added. In this pregnant darkness, head downward, I waited until I abruptly felt a slow cascade of water going up my nose … I held my breath for a while and then had to exhale and – as you might expect – inhale in turn."

That, he says, "brought the damp cloths tight against my nostrils, as if a huge, wet paw had been suddenly and annihilatingly clamped over my face. Unable to determine whether I was breathing in or out, flooded more with sheer panic than with water, I triggered the pre-arranged signal" and felt the "unbelievable relief" of being pulled upright.

The "official lie" about waterboarding, Hitchens says, is that it "simulates the feeling of drowning". In fact, "you are drowning – or rather, being drowned".

He rehearses the intellectual arguments, both for ("It's nothing compared to what they do to us") and against ("It opens a door that can't be closed"). But the Hitch's thoroughly empirical conclusion is simple. As Vanity Fair's title puts it: "Believe me, it's torture."