Kubica in action on his return to F1 action at the start of June in Valencia - Picture courtesy of Renault

"I can honestly say it's the most thrilling day that I've spent as a journalist watching F1."

It wasn't a race, and neither was it even an official test, but a sparse Ricardo Tormo circuit on the outskirts of Valencia playing host to a truly heart-warming sporting story at the start of June - Robert Kubica's return to an F1 car for the first time since suffering career-changing hand and arm injuries in a horrific rallying accident in February 2011.

In the newly-released August issue of F1 Racing magazine, Anthony Rowlinson tells the inside story of the test which has got Formula 1 talking - and now triggered what had long been considered the most unlikely of comeback attempts.

Picture courtesy of Renault

But what was it like to be trackside at Valencia when Kubica took an F1 car for a drive for the first time in six years last month?

"There was a level of quiet expectation going into it, but nobody really knew what would happen with Robert," Rowlinson told Sky F1. "Obviously he prepared, the Renault team had some simulator work with him, but nobody really knew until he got on track.

Kubica steps up F1 comeback bid

"I was watching from the garage and after one lap you could sense the feeling throughout the garage of 'oh my god, he's still totally got it'. There was that moment of realisation that still, despite the injury, and a very long and tortured rehabilitation process, he was still fully capable of driving a Formula 1 car at proper speed. You could feel it in the garage.

"From there the whole tone of the day changed from just being about putting Robert in the car to the sense that they are actually evaluating him properly."

Robert Kubica speaks to Sky Sports at Goodwood about his hopes of making a full return to F1 Robert Kubica speaks to Sky Sports at Goodwood about his hopes of making a full return to F1

They certainly are now.

Any expectation that the Valencia outing, when Kubica completed 115 laps, would prove a one-off has since been quashed by confirmation of a second test.

Renault will run Kubica, perhaps as early as next week, at a special session at the Paul Ricard circuit in France to "assess his capabilities to return to the highest level of competition".

This is a comeback attempt getting serious.

His pace in that initial test, which Rowlinson describes as quick and, even more impressively, immediate, has surely had something to do with it.

Anthony's feature on Robert's return features in the latest edition of F1 Racing magazine

Read the behind-the-scenes feature on Kubica's comeback test in the latest edition of F1 Racing magazine, which is on sale now.

In the F1 Racing feature, Rowlinson writes: "The day before, Renault reserve driver Sergey Sirotkin had lapped a similar E20 (the car with which, in Lotus livery, Kimi Raikkonen won the 2012 Abu Dhabi Grand Prix) here in 1min 14.6s. Kubica pops in a 1min 14.27s at one point during his morning run without apparent effort.

"He's back doing the thing he does best and once the initial frisson of concern as to his physical capabilities has passed, it's back down to business for team and driver. Unfinished business."

Post-Paul Ricard, the next step towards a full-on comeback would be a run in a 2017 car - with the early-August test in Hungary one such opportunity open to Renault should they, and Kubica, feel the one-time F1 race winner is ready to take it.

"If Renault put him in the car in Hungary, which would be a 2017 car against current drivers, I think that means they're going to have to stop being coy about it," adds Rowlinson.

"A private test at Valencia is one thing, a run up the hill at Goodwood another, but if they go that far then they are evaluating him properly."

For six years, F1 and its fans have pondered plenty of 'what if' questions surrounding Kubica and the career trajectory the Pole was on before his rallying accident. The next few months should give a firm indication about whether, against all odds, some of those questions could yet produce some answers.

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