Robbie says he'd recognise Dr Leir if he saw him. He has been a talking head on UFO documentaries Robbie has watched. And, sure enough, he spots him in the coffee shop adjacent to the casino. Robbie says he feels starstruck around UFO experts in the way other people feel starstruck around pop stars.

"Doctor," he says, "sorry, I'm Robbie. I saw you at the Conscious Life Expo. And I've seen you many times on the Discovery Channel."

"I've been a lot of places," Dr Leir growls.

"We've heard that you have a reptilian tissue sample here in the hotel," I say.

"Have you done any tests on it?" Robbie asks.

"I only got it yesterday," Dr Leir says.

"Can we see it?" I ask.

"Sure," he replies.

He takes us to his room. Dr Leir is the surgeon who claims to have extracted from patients 15 implants that are not of earthly metal. In the lift I ask if he has brought any of the implants to the hotel. He looks at me as if I'm an idiot.

"That would be absolutely ludicrous, unscientific and ridiculous," he barks. "I keep them locked away." We reach his bedroom.

"Where's the skin stored?" Robbie asks. There is a silence.

He produces it from his wardrobe. It is a tiny flake at the bottom of a jar. Robbie, Ayda and I crowd around and examine it.

"It could be a scale," I say. "It could be a reptilian scale - which is, of course, the hope - or it could be a little bit of a wing of a moth. Could it be a moth wing?"

"It could be a lot of things," Robbie says, cutting me off. "So, Dr Leir, this was given to you last night. Are you excited about what it may be?"

"In a word," Dr Leir replies, "no."

"Oh," Robbie says.

"It could be a piece of nothing," snaps Dr Leir. "I was recently sent an object that was surgically removed from an abductee. I put it under the electron microscope. It looked like an organic compound, so we went to the next level. We did a test that uses infrared spectroscopy. Long story short, it was a piece of wood."

"Ah," says Robbie, a bit disappointed.

"So I just spent $25,000 to look at a piece of wood," Dr Leir says. "You ask me if I get excited? No."

We fall into a slightly depressed silence.

"Do you worry that the aliens might want their stuff back?" Robbie asks, hopefully. "Do you get scared that they may want to come and get their transmitters back?"

"Well, if they want them back," Dr Leir says, "they certainly have an advanced technology over what we have. They could just take them."

And so ends our day at the conference. Robbie buys 15 UFO DVDs and we catch the plane back to Los Angeles. He puts the pile on the table in his TV room. They have titles such as UFO Space Anomalies: 1999-2006. I ask if he's really going to watch them all. He nods.

"I used to read the Sun, the Mirror, the Mail all the time," he says. "Eventually I had to stop looking because I'd find things that would upset me, whether it would be about me or about somebody else. So I had to fill that void. And that void has been filled with this stuff."

I think it's healthy that he doesn't look himself up in the papers any more. That week alone it had been falsely reported in the News Of The World that he had been dumped by a "Norwegian beauty" called Natassia Scarlet Malthe, and falsely reported in the Daily Star that he had been having secret face-to-face meetings with "mental conspiracy theorist David Icke" (they've never met). But the world he's obsessed with now - the UFO world - has its many liars, too.

"It's surely out of the frying pan and into the fire, liar-wise," I say.

Robbie nods. He says he knows that there is a chance it's all nonsense. "But even if it is all made up," he says, "it's better made-up stuff than what the tabloids are writing. It's more interesting. To me, anyway."

"And it isn't about you."

"Yes," Robbie says.

I leave him standing on his balcony with Ayda, and he does seem happy, gazing up at the sky, even if there's nothing paranormal up there.

"There's always this weird black circle," Ayda says. "You see that black patch over there? It's like dark fog."

"Yeah," Robbie says, "but that might be something as easily explained as light pollution." He pauses. "Right now I'm, 'You crazy American bitch! That's just light pollution!' But if we didn't have company, I'd be going, 'Let's stare at it for an hour and a half. Materialise! Materialise!' We'd be doing our materialise dance. But let's not do that while Jon's here. He'll think I'm weird." They carry on looking at the night sky.

"No," Robbie says, finally, "I don't think there's anything up there tonight."

· A radio documentary of their trip, Robbie Williams And Jon Ronson Journey To The Other Side, will be on Radio 4, May 6, at 6.30pm.

Copyright: The Guardian