@Stu Jones,
@MikeS,
@Griff
Shiver me timbers!!!
Thinking that maybe it was a Mac thing, I fired up an old PC notebook and discovered, quite by accident when clicking on the video to get it to start playing, that
double clicking in the middle of the frame directly on Griff expanded it. (or maybe this works anywhere within the frame)
Went back to my MacBook and, lo and behold,
double clicking on Griff worked on it, as well.
After doing a little research:
Simply pressing the "F" key on my keyboard does the job.