In July 2013 I was in the bowels of Nissan Europe’s Barcelona technical centre doing something rather innocuous. Or so I thought.

I was doing some early reporting under a long-lead embargo on the development of the second-generation Nissan Qashqai, for an article that wouldn’t be published until the following April.

As part of a whistle-stop tour of the various facilities and departments involved in the Qashqai’s development, the engineering whizzes took us into a chamber where they set the official economy and CO2 figures for their cars.

From the group of us visiting the facility, they wanted a volunteer to have a go at part of the test. My hand shot up the fastest.

So I have played a hands-on role in one of the infamous official economy tests. Here’s what happens. 

Before the engine even reaches the car to set the official figure, it is first fully tested, calibrated and optimised for economy and CO2 on various test benches and in lab conditions. At this point, it’s ready to go in the car.

The cars used are proper models rather than anything trick, although the Qashqai I was in was covered in camouflage wrapping because it had yet to be revealed to the world.