Kubica, a grand prix winner whose F1 career was interrupted in 2011 by a rally crash injury, drove a 2012-spec Lotus F1 car in a test arranged by Renault in Valencia earlier in June.

The 32-year-old covered 115 laps of Valencia's Circuit Ricardo Tormo and said after the test that he could now target a “proper comeback” to F1.

Speaking to Poland's Eleven Sports, Permane said that Kubica had shown good speed in the test – but reckoned that his mileage was the bigger surprise.

“I had no doubt on his pace, ever, at all,” Permane insisted. “I did not know, and I don’t think he knew, whether he would be able to drive physically – and, more than that, be able to drive a lot.

“He's driven some things. He’s driven simulators, he’s driven a GP3 car earlier this year in preparation for this, but we didn't really know what his limitations would be. And, honestly, it went very well.

“He was quick. He did some long runs, he did some short runs, he did qualifying, we did race simulations and it all went very well.”

Asked about the viability of Kubica's comeback target, Permane said: “From what I've seen from the statistics, from the data, the pace is there. That's for sure.

“All I would say is on that Tuesday in Valencia he done a fantastic job. There are many other circuits, and whether he has physical limitations on those, only he knows at the moment. If it needs to go any further, that would be the next step.”

Kubica's severe right hand and arm injuries from the crash had been a factor in keeping him out of open-wheel machinery over the past few years, but Permane said Renault only needed “a very very small modification to the steering wheel for shifting” to accommodate the Polish driver in the E20.

He added that he did not believe F1's recent switch to faster, harder-to-drive cars would hamper the Polish driver's comeback chances.

Wanted to avoid “media storm”

Kubica's Renault test had been in the works “for a few months” but it was only officially confirmed by the team only after it had taken place.

Permane explained: “Honestly we did not want to create a big media storm. We knew, once in got out, everyone would be interested. Everybody loves Robert, everybody feels very sad for what happened.

“Honestly he was very calm about it. He had no problem with telling people and that. I didn’t want to put a lot of pressure on him.

“I just wanted it to be a day for him, without any expectation, any pressure, just for him to drive.”

While Renault communicated that the test was a one-off, Permane has confirmed the outfit was open to giving Kubica further opportunities.

“I think its too early to comment. We’ve still been in touch, we've been talking about anything possible we might do in the future.

“At the moment there is nothing else planned, I can say that much at the moment. But I wouldn't say we won't do something again in the future."

On whether having him in the team's simulator at Enstone was an option, Permane said: “I know he’s driven some other simulators, and maybe that is something we will be thinking about for the future. That might be the next step, is to go into simulator.”