Fortunately, cars rarely leave the road at a rally, and when they do it usually ends harmlessly. In an ideal situation, the driver and co-driver land in the ditch, field or bush next to the road. However, every so often it goes horribly wrong, resulting in the car coming to an abrupt stop against stone walls, trees or barriers. Some of the most spectacular scenes in rallying occur when the car takes off and rolls. In this case, it is immediately clear that something has gone horribly wrong.

Sometimes the driver overestimates his own ability, does not take a section seriously enough, or completely underestimates it. However, sometimes it is down to a mistake made during preparations for the rally. The first official part of any WRC rally is the two-day "reconnaissance" – a series of track inspections carried out by each competing team and known in the trade as the "Recce".

The crews drive the individual special stages in a production car. Cars competing in the rally are not allowed on the Recce. A WRC speed limit (90 kilometres for tarmac rallies, considerably less for rallies on gravel) is enforced and monitored by a GPS system in the Recce car. Exceeding this top speed is penalised by the WRC. The teams use the "Recce" to put together their pace notes. These are one of the most important elements for the entire team and can ultimately make the difference between success and failure at a rally.

How does the Recce run then? "Driver, co-driver, and often the team boss and some engineers are often involved in the reconnaissance drivers," says Paul Nagle, co-driver for Kris Meeke in the MINI WRC Team. "We travel in a modified production model of the MINI Countryman but which also has a roll cage and the seats used in the MINI John Cooper Works WRC for example. On the first run, the driver dictates the pace notes to his co-driver just as he would wish to hear them during the rally itself. The co-driver takes down the driver's instructions and notes the points at which they must be read."

On the second drive through the special stage, the co-driver reads the pace notes back to the driver – a kind of reassurance that no mistakes were made when writing the pace notes. "It is still possible to correct or refine the pace notes here, or to add further details regarding the course," says Carlos del Barrio, who gives the instructions to driver Dani Sordo in the MINI WRC Team.

While the driving team are working on the pace notes, the rest of the Recce team is busy gathering information on how the car must be set up and what strategy to adopt for the course. At the same time, a video is taken of the course, in order to be able to see a special stage again in detail at a later date. The co-drivers also discuss any prominent sections of the course among themselves. "Carlos and I spend a lot of time analysing the course together," says Paul. "We are a real team."

However, the co-drivers' work begins before the official Recce. "We have already been on-site for one or two days beforehand," says Carlos. "At that time you are not allowed on the actual special stages themselves, but we are able to take a look at the location of the service areas, certain sections of the course where you can access service areas, and points where you can stop during the Recce." The drivers are not usually present while all this is taking place. The on-site preparations usually take the co-drivers hours before they continue to work on the data in their hotel rooms.

Four weeks before the event, the organisers of the rally provide the teams with comprehensive maps of the course. The route is compared with that of the previous year. Any changes to the route (about 30 to 40 percent is changed each year), for which completely new pace notes must be made during the Recce, are indicated. "The most difficult part of the preparations is when there is something new on the route," says Carlos. "It is all a lot easier when you are competing at an unchanged rally for the second or third time. However, you have to give 110 percent the first time."

It is a matter of perfection. The driver and co-driver must work flawlessly as a team when it really counts. When it comes down to it, the driver must trust the instructions from his co-driver one hundred percent. "When I say we are approaching a gentle right-hander that we can take a full throttle, Kris steers right at full throttle," says Paul. And what happens if the pace notes are wrong or the co-driver has missed a line and the car is approaching a sharp left-hander that requires heavy braking instead of the gentle right-hander. "Too bad," says Paul. "Kris will steer right at full throttle." It is not hard to imagine the outcome.

Carlos del Barrios put together no less than 300 pages of pace notes for the 2011 Rally Germany, which he had in his lap on every special stage in the form of a book – and this is by no means the longest pace notes in Carlos' career. "The 1994 Rally Portugal was the worst so far," he recalls. "There were 36 special stages and 34 of them were new. The average length of the pace notes for each stage was about 30 pages. All in all, the pace notes for the rally were about 1000 pages long."

This amounts to a lot of paperwork that must not only be completed by the start of the rally, but must be correct right down to the smallest detail. And all this by hand and new every year. No wonder the co-drivers spend just as much time at their desk as they do in the passenger seat.

In the end, however, it is worth the hard work. Winning a special stage or even overall victory at a rally is not only the result of perfect preparation and excellent teamwork, but also the best possible form of compensation for the effort involved in the painstaking preparations, which often begin months in advance. And if it does not work perfectly? "Then we learn from our mistakes," says Paul. "And then it all starts from scratch again."