THE Volkswagen American emissions cheat scandal rumbles on and leaves me completely astonished that one of the world's most trusted manufacturers could even think of getting involved in such a mess.

There are millions of Volkswagens affected worldwide and now it seems that some 2.1 million Audis are affected too, with 1.42 million in Europe.

The Czech arm of VW, Skoda has also said that 1.2 million of its cars are affected.

Sicne the so-called Dieselgate scandal broke I have been asked coutnless times what the problem is and from what I can gather it involves a piece of software in the computer of the affected cars.

It all came to a head in the USA where the Environmental Protection Agency found that some VW diesel cars embodied devices that could detect when they were being tested, changing the performance accordingly to improve results.

It seems that the guilty software can sense test scenarios by monitoring speed, engine operation, air pressure and even the position of the steering wheel.

When the cars were operating under controlled laboratory conditions the device appears to put the vehicle into a kind of safety mode in which the engine runs below normal power and performance.

Once on the road the clever device switched the car from the test mode emitting nitrogen oxide way above the stringent US limits. Fiendishly clever but completely against the rules in the USA.

VW boss Martin Winterkorn has resigned but denies any knowledge of the device - but someone had to give the OK to such a dark piece of technology.

I await with interest to see the result of the VW blame probe and also to see if any other manufacturer has developed such a device to boost ailing American diesel sales.