I produced a video review of the Australian made, Saracen Ultra Trailer Hitch Lock by Purple Line, you can see it listed at the bottom of this post.
P.S. This is not the cheapest Trailer Hitch, but I consider it the Best on the market today.
If you fast forward to the 4.07 minute mark in this video, you will see a split screen demo of my hitch lock in action, its attached to a tow vehicle, and trailer.