We don't believe it - and to this day we haven't met anyone who could do it!!!

Do you have doubts? - Don't take it too seriously, because here Werry exploits a pun that arises from a minor linguistic slip-up:

You hold a red silk ribbon and hand a spectator a white plastic ring about 8 cm in diameter. Ask them if they can tie the ring onto the rope while you hold the ends.
Before he can answer, you continue: "No, you can't. No one can do that --- except me."
You place a sheet over the center of the band, and a spectator holds the entire thing. Then you have the ring returned to you and place it under the sheet. A second later, you pull back the sheet, and sure enough, the ring is now on the band— knotted!

But not in the way the audience thought, but exactly in the sense of the question posed at the beginning:

The ring is knotted onto the rope and not the other way around, as every observer would have expected !