A couple of weeks ago, the London Government dropped proposals to make vehicles pass MoT tests every two years instead of annually.

Unsurprisingly, safety campaigners had opposed the move, but the Government still has a bee under its bonnet about MoTs.

Transport Secretary Justine Greening has been hollering about ensuring the tests are carried out properly. (The situation is different in Northern Ireland where there are government-run MOT centres).

Good call. Her department's research found that defects were missed in a quarter of vehicles tested in 2010-11. No one will be surprised by this. Garages are like mysterious black holes. You put your car in and have no idea what they're going to do it or how they arrive at the massive sums needed for essential repairs. You have to take it all on trust.

But what do they actually do in an MoT? The only comprehensible part of the scrap of paper they give you concerns emissions. Fine. Presumably something to do with the environment. Often enough, they'll say you need a new tyre.

After my car's recent MoT, I was told it needed one of these. So I stumped up and, when I drove the car away, it kept pulling hard to the right.

They hadn't aligned the wheels. When I took the car back they were just having a wheel aligning machine delivered.

They hadn't even had one on the premises when they did my tyre. I also had to get the lower suspension arms replaced. All of which cost hundreds of pounds.

A week later, the car broke down and had to be towed to another garage by the RAC, which doesn't seem to bother fixing anything by the roadside now, even though that's what you pay them for.

The auxiliary drive belt had gone and the car needed a new water pump. I, meanwhile, needed artificial resuscitation when I learned this was going to cost further hundreds of pounds.

All together, since taking my hitherto happy wee car in for an MoT, I was now nearly a grand down within a week.

There was even a suggestion that the work carried out on the MoT repair had contributed to the second fault. Even if that wasn't the case, why wasn't the second fault - which involved a potentially fatal loss of steering - not picked up during the MoT? Isn't it part of it? If not, why not?

What is the MoT and what exactly are they looking for? What's the difference with a service?

All anybody knows about the latter is they charge you a fortune for changing your oil - which, on one occasion with a previous car, was found to be empty a couple of weeks after a supposed service. Few of us know or care about car engines. We just want to ensure our cars are safe. So why not take the mystery and ritual out of this?

Why not have one big test every year that checks your car, tops up what needs topping up, and guarantees the vehicle is roadworthy?

We won't mind paying for the peace of mind. And at least it'll stop the riddle-shrouded garage industry driving us mad.