I hope he doesn't say it was aliens. That one's been done to death as well.
Erik Von Danneken. When I was in fifth year in school in the 70's, I read all his books and was a complete devotee. Told everyone in school and my family to watch the Horizon special on him that was coming up. They ****ing destroyed him. I screamed conspiracy for a few weeks, but just had to give up in the end - no science whatsoever to back up his claims.
But the best I remember was the Inca drawings, that he said in his book could only have been done with directions from an altitude of 30k feet: then some archaeologist, who'd studied them all her life, patiently explained how and why they did them. They worshipped sky gods and were, like a lot of ancients around the world, more mathematically competent and ingenious than we like to give them credit for. Just because we lack the skills to do any of this without computers and powered mechanical aids nowadays, that doesn't mean they couldn't. It's like doubting hunter-gatherers could feed themselves as they didn't have Tesco's back then.
She was always more interested in pseudoscience than the real thing.