At this moment in time, only 1 of my cars has a valid MOT and it was the only one that didn't deserve one. It had to be one of the dodgiest MOT I have ever encountered, and was only 3 weeks old when I got the car.
It was physically impossible for the rear brakes to have been working at the time of the MOT, and the handbrake was also totally inoperative. The outer headlights were both faulty (something wrong with the halogen replacement units, they did not have any discernible light pattern)., worn out suspension bushes, removable jacking points (rusted away round the outside) and numerous other minor things
I went over the car with a fine toothed comb but someone else could have just driven it round as it had an MOT oblivious to it being possibly lethal.
So having an MOT isn't everything.
Nearly all the issues now sorted ready for a more legitimate MOT later this year by the way.