Educating your children in the olden days used to be so much easier. You packed them off to whichever boarding school was furthest from where you lived, with some simple advice: “See you in five years, son, and try not to get sodomised too much.”

Public schools back then had to prepare boys for a life that would see them squatting in a muddy trench being shot at, or dying of diphtheria in some far-flung corner of the empire. So the school had to be as uncomfortable and as sadistic as was technically possible. There needed to be 10-mile runs through minefields and executions for those caught, as John Cleese put it, “rubbing linseed oil into the school cormorant”.

You may have read a short story by Roald Dahl called Galloping Foxley. It chronicled Dahl’s time at school: the bullying, the sub-zero humiliation and the terror. Well, I was in the same house at the same establishment 50 years later, and I endured much the same sort of thing.

I was flung into unheated plunge pools in the middle of February and used as a goalpost in games of bicycle hockey. Younger boys were made to do all the cleaning and those who failed to do it properly were beaten with whips, strangled, stabbed, sodomised and drowned. Once I forgot to empty the bins and was eaten.

Then, as a real preparation for the astonishing unfairness of life, when I reached the sixth form and was licking my chops at the promise of being able to kill and eat a young Canadian boy for having an annoying whiney accent, fagging, bullying and murder were banned.

It was the start of the slippery slope down which it seems all public schools have now tumbled. Today you don’t prepare boys for a life of misery. You have to prepare them for a life of 24-channel, hot-and-cold-running luxury, and as a result the great and the famous educational establishments seem to be competing, not for which can be the most brutal, but which can most closely resemble Claridge’s.

I looked round a couple of the big ones last week and couldn’t believe the metamorphosis. There were cleaners doing the cleaning and exotic Thai dishes on the menu — the menu, for God’s sake. There were carpets, and fire extinguishers that worked. The lavatories had doors. There were trout lakes, and the mattresses on the beds were stuffed with feathers rather than horse fur and dead fags. Most of all, though, some of the boys wore skirts and had breasts.

One thing hadn’t changed, though. Parents (ie, me) are still turning up in expensive cars they’ve borrowed for the day.

When I was at school we had the local bobby check the registration plates on all the visitors’ cars and you wouldn’t believe how many were from rental companies. On one speech day we calculated that a full 25% of the motors had been hired by mums and dads who obviously felt their own wheels were too downmarket.

They probably felt good stepping out of the Avis Cadillac or Hertz Jag, but the elation rarely lasted since, as a punishment, we liked to fling their sons from the top of the church tower. One father arrived at the end of term in a chartered helicopter, which we thought was so obscene we took his son round the back of the cricket pavilion and set fire to him.

Public schools were, and always will be, anti-chav. They are bling-free zones where uniforms must be second-hand, watches must be broken, stereos must be wooden and cars, ideally, must be Subaru Legacies.

All of this came flooding back last week as I nosed into the genteel quadrangle of a traditional school, which shall remain nameless, in an egg-yellow Porsche 911. That wasn’t mine.

You could see the sneers on the pupils’ faces. You could see them making a mental note that when my child starts there he will be made to pay. I doubt, in these softer times, that he will be murdered but they may well chop up his teddy bear. And it’s all my fault. A Porsche 911 is bad enough. But an egg-yellow Porsche 911 with “Porsche GB Press Fleet” written below the terrifyingly personalised numberplate. That, quite simply, is as low as you can go.

Or so I thought. The next day, to get to another school, I inadvertently climbed into a Mini Convertible with stripes on the bonnet. This would have been like turning up at a black-tie cocktail party dressed as a 6ft banana, so I parked it in the next village and walked.

What’s desperately annoying is that I had the perfect public school parent car parked in the drive at home. It wasn’t a Subaru but a silvery grey Audi S4 Cabriolet. One of the most tasteful, unassuming and beautifully made cars money can buy. Yes, with four-wheel drive and a V8 engine, it’s as lively as an Ibiza discotheque, but from the outside it’s no more ostentatious than a Regency town house in Bath.

This car really is very fast. There’s no V8 burble, no vulgar-sonic Route 66 soundtrack to attract attention, just a relentless whine to accompany a blurring of both the hedgerows and the speedometer needle. And then, before you know it and with seemingly no effort, you’re doing an indicated 155mph and being prevented from going any faster by the electronic limiter, put there to keep the Green party happy.

Even at high speeds the electric roof doesn’t lift or flap and nothing rattles. And with it down there’s space for a family of four to enjoy a buffet-free cruise. In so very many ways, then, this is a great car. Practical, well made, fast, silent, stylish and cool. There are very few cars that do quite so much quite so well. So why, you may be wondering, did I not use it?

Well, behind the veneer of sophistication and brilliance it is badly flawed. First of all, I couldn’t get comfortable. If I arranged the seat so my legs could reach the pedals the steering wheel was too far away, and if I sorted out my arms I could only go a mile before cramp started to solidify my right calf. I’ve never noticed this in an Audi before but my cameraman, who’s also long, says he suffers from exactly the same thing in his A3.

And it’s not just the driving position that makes life miserable. I know I’m starting to sound like a stuck record but Audi has absolutely no idea how to tailor a car to accommodate the sloppiness of Britain’s roadworker Johnnies.

Where an S-type Jaguar glides and floats over potholes and ridges the Audi crashes and judders. The ride comfort is simply appalling. On one dip, where the A40 joins the M40 just outside Oxford, I really thought it was going to take off.

On a smooth track the hard-top S4 handles beautifully, and I have no doubt the cabrio would be similarly impressive, but the price you pay for this is too high and not necessary. BMWs handle without being uncomfortable. So do Jags and Mercs. So Audi must find the people responsible for this shortfall and, at the earliest possible opportunity, throw them in an unheated lake.

The people who did the satellite navigation system should go, too. It’s very clever, shoehorning the screen in between the speedo and rev counter, but with no map it doesn’t work. With no map you can’t tell how far off the route you are until you’re in Snowdonia.

Over the course of a week, this car drove me mad. Think of it as a shepherd’s pie that’s too salty, or a wonderful holiday resort that’s full of German taxi drivers. It was so close to perfection and yet so very, very far away.

That’s why I left it at home and that’s why I went in the Porsche, and that’s why my children are going to spend five years at school with no teddy bear.

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