Despite Zak Brown's call for a thorough, historic investigation, FIA says its investigation into Red Bull's ride height device has concluded.

While the FIA had said there would be no further action over the device, the McLaren boss, still unconvinced by its effectiveness, called for a historic investigation in order to discover how long Red Bull had been using it for.

However, the FIA's Head of Single-Seater Matters, Nikolas Tombazis insists that the case is closed and that there will be no further investigation.

"I mean, honestly, can I say with complete certainty about whether there's ever been anything irregular? No," said Tombazis on Saturday. "Can I say that the matter is closed? Yes, absolutely," he added.

In terms of a historic investigation, he said: "To go and retroactively actually prove exactly what has happened before is difficult, and we don't think we have the ability to go and investigate two years' worth of situation," he said

"Generally, when we decide to escalate the matter, and go to the stewards or tribunal or whatever, we want to have some reasonable indication, not based on hearsay or just speculation," he added.

"As the design is not illegal, we believe that the correct action is to say: 'Well, okay, certain things need to happen in order to guarantee there's no ongoing sort of concern.' But we also have to also draw a line in time and say that there are certain things we can't go into much more detail with."

Referring to the suggestion that CCTV footage be analysed in order to discover if the deice was being activated, he said: "People are allowed to check things on the car, and it's a matter of how easy that is.

"If you have to dismount the whole bodywork and do fifty things, then obviously it would be visible in the camera. But on something as simple and as quick as that, I don't think you can realistically check that on cameras or virtual images or so on."

Amidst claims that the sport's governing body should take a more radical approach, such as encouraging whistle-blowers, he said: "We need to always consider that we're dealing with humans. We're dealing with humans changing conditions: with loyalties , old loyalties, and new loyalties. So, one has to be a bit careful about how you escalate that.

"We also don't want to be fitting lie detectors on people and doing interrogations under bright lights, or something like that. That is not what we want to do here.

"I've obviously worked in the past in teams, quite a lot, and I've employed people from other teams. I think there's sometimes a tendency to say, well, where I came from, we were doing XYZ.

"Sometimes one has to really interpret these comments very, very carefully. You cannot just base an escalation on a few comments like that."

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