How to Fix “There is no connected camera” Error on OSX Mac FaceTime or PhotoBooth

For the first time ever today after using various Macs for 10+years, I was suddenly met with this screen upon launching FaceTime:

there-is-no-connected-camera-osx-mac-warning

How to fix this?

A restart (as with most things) sorted it out for a short while, but the issue returned again after the next time that the system re-awoke from sleep mode. A little Googling suggested running the following commands in turn from a Terminal window:

sudo killall VDCAssistant

and then after that, this:

sudo killall AppleCameraAssistant

And that’s seems to do the trick!