The main claim to fame of the highwayman's hitch is that it can be quickly untied by pulling the short end. The knot just slips out of the ring. It's an easy way to cast off without having to untie a knot by hand. It is not intended to be a very solid knot but really a convenient way to tie up to a dock before going sailing.
I use this knot when I am alone to cast off in my Skerry. After tying the knot I drop the end of the line to where I sit in the boat. I can easily pull it and cast off.
Tying a Hywayman's Hitch
A loop goes through the ring, then from the boat side of the rope another loop is formed and gets slipped into the first loop. From the working end (the left side) another loop is formed and slipped into the second loop. At that point you can tighten the knot and it will hold. I like to add still another loop from the short working end. When you want to until all you need to do is pull on the working end (on the left of the illustrations) and the knot falls off and away you go.
I guess you could release a horse and run away fast if you were a highwayman.
Don't use this knot if you are not staying near or if the conditions are rough and there is lots of pulling, or if the line you are using is really slippery or stiff. I also watched this knot come apart after the loose end of a fairly heavy line fell in the water and was bobbing up and down and sort of pulling on the knot. After a few minutes the knot had come undone.
This web site reflects my personal ideas and doesn't represent anyone else's point of view.