He says he was the target of an intelligence operation, that a colleague of his was subjected to mind-control experiments and that he received a personal safety warning after talking to an engineer about a spacecraft.

Delonge - who's regularly discussed his conviction that aliens exist and UFOs are real - tells PaperMag.com: "I've had one interesting thing happen to me where I believe somebody was trying to get to me, that was in the intelligence industry. That's as much as I want to say. A very interesting thing happened."

He adds: "One time I remember bringing up a very specific craft that I believe we're building, in secret, to emulate the phenomenon that our government has been observing for decades.

"I started talking about the craft, its magnetic slide system, how it ionises the engine, how it glows. I went through the whole thing, and this engineer looks at me and goes, 'You better be real f***ing careful about what you're talking about.' I go, 'Okay, so I'm close.' He goes, 'I'm not f***ing kidding with you. You better be really f***ing careful.'