Back in 2016, Ferrari, Mercedes and Red Bull took part in a special "mule car" test programme to help Pirelli with the development of its prototype wider tyres.

They happened to be the three top teams of the current era, so with or without the rule changes it was inevitable that they would also remain the dominant forces in 2017.

But did that test programme give Ferrari a crucial boost that has allowed the Italian team to take on Mercedes head-to-head this season – and helped Sebastian Vettel to hold the championship lead 11 races in?

It’s obvious that Ferrari’s improved form has resulted from progress in all areas, with marginal gains adding up to overall upward progress.

But tyres have clearly been a key element, and it’s apparent that Ferrari has usually enjoyed an edge on tyre management, certainly in the first part of the season – notwithstanding the issues at Silverstone, which were seemingly down to bad luck.

Sebastian Vettel, Ferrari tests the 2017 spec Pirelli Photo by: XPB Images

How to make testing fair has been a perennial problem for Pirelli. When it started its original F1 development programme, it was able to ensure a level playing field by utilising the neutral Toyota TF109, handily available after the Japanese manufacturer pulled out of the sport.

When that chassis had passed its sell-by date, Pirelli had to cast around for a more up-to-date car for 2012, and it settled on a Renault R30.

That seemed like a suitable solution for the big guns – at the time the Enstone outfit was not a threat for race wins, having finished a distant fifth in the 2011 championship on 73 points. In effect, it was the team furthest down the order with the capability to run a test programme.

In the hands of Lucas di Grassi and Jaime Alguersuari, that car ran five test sessions at Jerez, Spa, Barcelona and Paul Ricard in 2012, for a total of over 7000kms. Pirelli did its best to ensure parity by giving all the competitors reports and data from the tests.

Nevertheless, some teams were concerned that the re-badged Lotus team would gain an advantage, even though its own drivers were not involved in the testing.

The stats did little to allay those fears: from 73 points in 2011, Enstone scored 303 in 2012 and 315 in 2013. Was that just the Kimi Raikkonen effect, or had its involvement in testing, at a time when it was so restricted, given the team extra inside knowledge of the tyres?

F1 Pirelli Test: Jaime Alguersuari Photo by: Pirelli

It was that sort of suspicion that Pirelli (and the FIA) desperately wanted to avoid when planning the test programme for the 2017 rules.

The added complication was that the tyres would be wider and would have to deal with much higher downforce levels, so it wasn't just a question of bolting them onto an existing car.

The solution was the "mule car" package: a 2015 chassis adapted for the wider tyres and with high downforce added to approximate the 2017 loadings. All teams were invited to tender, and not surprisingly the big three – Mercedes, Ferrari and Red Bull – agreed to take part.

They each had the resources to build and run a special car during a season already made busy by preparations for the new rules. None of them wanted to be left out, because they all knew that taking part would confer some advantage. So why let a key rival steal a march?

The workload was carefully split between the three, who were each given the same number of days and the same opportunity to try all the tyres in the range, plus wets, culminating in a final verification test in Abu Dhabi where all three cars would run.

In conjunction with the FIA, Pirelli went to great lengths to ensure that the three teams did not gain an advantage over those not involved.

The testing was "blind," with teams and drivers not told what they were getting. Data was shared between all teams, and rivals could send an observer to any test if they wanted to.

Max Verstappen, Red Bull Racing testing the new 2017 Pirelli tyres Photo by: Pirelli

The FIA also tried to ensure that running high downforce did not contribute directly to 2017 aero development by mandating that the mule car aero package did not reflect the new rules.

"The point is the mule cars were developed avoiding any solution that could give an advantage to the teams," said Pirelli F1 boss Mario Isola.

"So instead of developing the floor, the wings, and all the changes in the aero package of the current cars, they were obliged to use the skirts, old technology, and this kind of stuff.

"I have also to remind you that all the data were available to all the teams. Also some data related to the set-up of the car, like weight distribution, aero distribution and mechanical balance, were included in the report.

"All these data were available to all the teams, and the teams started to analyse the data, and tried to anticipate the tyres."

One of the most intriguing aspects of the testing was the identity of the drivers. It was clear from very early on that Ferrari was using its race drivers to a greater extent than the other teams. That was a signal that Maranello, and in particular Sebastian Vettel, believed that there was something to be gained.

Famously, Vettel was the only F1 driver to visit Pirelli's base and sound out the engineers during the build-up to the Italian company's return to the sport.

He also showed his commitment in 2010 when he won the world championship in Abu Dhabi, flew to Europe for a whirlwind victory tour, and then returned to the Middle East to sample the new Pirellis for the first time.

This is a man who, like countryman Michael Schumacher, leaves no stone unturned.

Long after it became apparent that Ferrari had come to the conclusion that focussing on its race drivers was a good idea, Mercedes resolutely stuck to using Pascal Wehrlein, at that time a Manor driver.

Pirelli tyres Photo by: XPB Images

Towards the end of the year both Lewis Hamilton and Nico Rosberg were asked if they thought they were missing out by not following Ferrari's example and doing the bulk of the testing. A shrug of the shoulders and puzzled look was the answer: amid their title battle, they didn't see the point.

Both did get involved, although Rosberg's session was spoiled by rain, and Hamilton made only a token appearance before he felt unwell.

Red Bull race drivers Daniel Ricciardo and Max Verstappen also only appeared right at the end of the programme, having left the bulk of the work to Pierre Gasly and Sebastien Buemi.

Pirelli's own figures for kilometres completed by each driver tell their own story:

Driver Team Distance complete (km) Pascal Wehrlein Mercedes 3,248 Pierre Gasly Red Bull 2,494 Sebastian Vettel Ferrari 2,228 Sebastien Buemi Red Bull 1,190 Kimi Raikkonen Ferrari 1,054 Max Verstappen Red Bull 517 Esteban Gutierrez Ferrari 480 Antonio Fuoco Ferrari 478 Nico Rosberg Mercedes 209 Daniel Ricciardo Red Bull 200 Lewis Hamilton Mercedes 50

Fast forward to 2017, and Ferrari has not only been super competitive, but the SF70H has been consistent, with a wider operating window than its main rivals. The team has adapted to the new tyres with apparent ease, certainly compared with Mercedes.

So did Ferrari gain more from the mule car testing, and if so, how?

It appears that the team simply did a better job of learning from the high-downforce running, and transferring that knowledge into the development of the 2017 car.

It's been suggested that the Ferrari mule car pushed the limits when it came to aero, and some elements did specifically help the team prepare for the new regs, despite the FIA attempting to stop that happening.

Ferrari also used the mule car testing to properly correlate the Maranello wind tunnel for high downforce and wide tyres, something that both Mercedes and Red Bull have struggled with in the early part of this season.

Then there's the question of the tyres themselves. As noted, the testing was blind, in that drivers were not given details about what had changed from test to test, or set to set. But they could follow the general trends.

Sebastian Vettel, Ferrari SF15-T Photo by: Pirelli

"With this big change in regulation, and this big change in our philosophy of making the tyres, they had the feeling of the direction at least," said Isola.

"One of the comments which was common after each test – when we were testing the new prototypes, they didn't know we were testing new compounds or constructions – but when we were testing the new compounds the difference was so big in terms of not overheating, they could push on the new compound, they felt immediately.

"When they finished the run all the drivers came back saying, 'Wow, we like these tyres, because I can push, I don't feel overheating, also if I overheat the tyre a little bit because of the sliding, I slow down a couple of corners, and the tyre is back.'

"That was a comment that was quite common. And obviously we were looking for a tyre with these characteristics. So it is clear that we took that direction."

Obviously, all drivers who took part in the testing, especially in the latter stages as the definitive 2017 specs emerged, could benefit from the running.

But Vettel and, to a lesser extent, Raikkonen were involved pretty much all the way through, and thus they could properly follow the development path, and just possibly, direct it.

Inevitably a driver of Vettel's calibre and experience must have an influence when he gets out of the car and says the equivalent of 'Eureka!' to the Pirelli engineers when he finds a tyre that is just so.

No disrespect to the likes of Wehrlein or Gasly – the two drivers who did most of the testing for the other teams – but if you were Pirelli, whose opinion would you feel carried more weight?

"The experience of a race driver who is a four-time world champion is obviously valuable, this is clear," said Isola. "A driver has sensations, feelings, when he drives a car.

"In F1 we are lucky, we have a lot of sensors, so we can basically replicate or check if the feeling of the driver is in line. I think it's more related to experience, because Pascal for example was doing a very good job, he was always available, and giving us good feedback.

"Sebastian is a professional driver, and when he was testing, after each run, he was giving us a lot of detailed information, his opinion on each set. 'I like this, I don't like that,' for this reason, that reason.

"The other drivers did the same, and we also had some sort of form they had to fill in, to not forget any detail.

"Obviously a driver is trying to push you in the direction of the tyre that he likes. When he was finding a tyre that he liked, it was, 'This is a good tyre, a nice tyre,' but the test was blind. So he doesn't know if at the end of the day if we selected the tyre that he liked or not."

There's no doubt that all three teams attempted to use the testing to gain an advantage, and intriguingly Red Bull admits that it didn't work as planned.

Christian Horner is adamant that Red Bull thought it had a handle on things and tailored the RB13 to suit, and then the spec of the tyres changed.

"I think actually running the Pirelli mule car hurt us in a few ways," he said. "A few things changed late on with the tyres that we potentially were designing the car around, that then changed. I think that may have perhaps influenced our development direction.

"I wouldn't say it backfired, but it definitely led us in a direction that wasn't conducive to the tyres that were ultimately nominated. The simple facts are that Mercedes and Ferrari did a better job of interpreting those regulations than we did over the winter."

Horner may flag up Mercedes, but Toto Wolff is equally frustrated with the way the mule car testing panned out.

He admits that it would have been better for Hamilton and Rosberg to have done more mileage - and while the German isn't racing this year, his input would still have been valid at the time.

However, Wolff says it seemed logical not to distract them from their day jobs.

"We were in the middle of that internal championship fight," said the Mercedes boss. "Where it's understandable that none of the drivers wanted to spend a lot of time looking at future technology and tyres, and rather focus on their own championship campaign. I think now in hindsight…

"In F1 you very rarely find a silver bullet that is going to make all the difference. But it is about putting all the marginal gains. And maybe, and it's just a hypothesis, I don't know if it's true, Sebastian's credibility and feedback to Pirelli can have an impact.

"And I don't think that the drivers would have particularly learned, but Pirelli's going to rely more on the results and on the feedback than from a junior driver. Having said that, we haven't got the data that supports that hypothesis."

Nevertheless, it's an idea that he's happy to put out there. The likelihood is that the 2017 championship will be won by a few points, with a bad race here or there – such as Hamilton's in Monaco – proving decisive. If Vettel does stay in front, then those marginal gains will have proved their worth.