It was done by Christian Hoverath and measured by cyclometer. I think it was actually 29.3 or so. If you knew him, you would know it’s believable. He expected to crash but didn’t and was very happy and I think he vowed never to again go so fast. I wasn’t there when he did it but he is trustworthy and told me personally about it.
There are lots of threads discussing this. See Fastest speed on unicycle or unicycle speed record
—Nathan