.......if an officer is so minded.
That is the bit I don't like. Too many laws seem to be subject to interpretation and depending on whether or not said officer has had a bad day, or a row with his wife, or is just plain stroppy, you may finish up with a fine that is not really justified. The beak will usually uphold the position of the said officer so unless you can afford a top QC you will probably loose if you try to fight it.
I do speak from personal experience, all be it 50 years ago. The charge was "dangerous driving" and I had a certain amount of un-confirmable evidence that not only did the said officer not follow me on the section of road stated but also had a gripe with the company where I worked.