First, you cannot just slap a tax disk on it and hit the highway. That would be too logical. No, you must first subject your vehicle to something called a MOT test, even if the car is a 1929 Bentley that was built before the MOT existed. The law doesn’t care about history.
This is the moment you find out if your car is a golden chariot or a sad, rusty toaster on wheels. You’ll pull into the test center, and the mechanic will look at your machine the way a chef looks at a burnt pot. Expect him to sigh.
Surprising fact: A car can be SORNed for decades, start on the third try, and still pass its MOT. Alternatively, a car that was parked for a week can fail because a bird looked at the windshield funny. The MOT god is a fickle deity.