We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "dennis@home"
saying something like:

The poster didn't actually say his old MoT had run out, did he?
You can get a vehicle MoTd as often as you like.

Its still an un-roadworthy car if it fails, or did you miss that?

No, it's not necessarily.
You ought to learn the difference between 'unroadworthy' and 'MoT
failure'.