The focus of this thread seems to be incompetent or ignnorant owners.

Twice in my driving history my life has been put in danger by incompetent professionals - in one case a garage mechanic who didn't put my car back together properly, the other a fitter at a tyre company who adjusted the tracking way, way off what it should have been.

I had my tracking set at a tyre company some years ago and found about a month later that they had not bothered to tighten the locking nuts against the trackrod ends.

Could any tester past or current answer my question as to whether or not a tester can issue some sort of prohibition notice for a vehicle found to be in this condition?

I'm not a tester, and haven't been one in the past, however this comes from a friend who is one ...

An MOT tester can issue (on your MOT failure) a 'Dangerous to drive' notification. If they do, then they will point out the dengerous points, and why they feel they are dangerous. The fail is obviously logged on the VOSA database. However, they cannot stop you from taking your car and driving it away.

Though they could phone the police as you did so.

Thanks for that info-seems funny that the system that was set up to prevent the use of cars in a dangerous condition cannot stop a dangereous car being driven away from a test centre!!

J1 Prohibitions General 1. VOSA's Examiners and specially authorised Police Officers have the power to issue prohibition notices (PG9) to prevent use on public roads of any vehicle found to be defective. In serious cases the prohibition has immediate effect, but in less serious cases, its effective date may be delayed for up to ten days

That is for VOSA's own examiners (i.e the people who conduct the roadside checks, usually along with the police). It does NOT apply to 'normal' MOT testers in garages.