'Almost impossible': Kubica's F1 astonishing comeback

Eight years ago, supremely talented Polish driver Robert Kubica's right arm was partially severed in a horror rallying accident that brought his Formula One career to a dramatic halt.

But racing is in his blood and he never gave up on his dream to compete again at the pinnacle of motorsport and on Sunday his astonishing comeback will be complete.

The 34-year-old will be on the grid in Melbourne for the opening Grand Prix of the year with a struggling Williams team in dire need of someone with such unshakeable determination to help reverse a worrying slump.

"It has been a challenging journey to make it back to the Formula One grid, but what seemed almost impossible is now beginning to feel possible," he said when he was announced as a Williams driver.

Before his accident, Kubica was touted as a future champion, with blistering natural speed and racing intelligence to rival his peers at the time Lewis Hamilton and Fernando Alonso.

He got his start with Sauber and won the Canadian Grand Prix in 2008 before moving to Renault.

But this is a new era and how he fares, and whether he still has the capacity to perform miracles with an underperforming car, remain to be seen.

His preparations have not been ideal, with Williams missing the first two days of pre-season testing in Barcelona last month. Although the Pole managed plenty of laps his time was well short of the front runners.

"Out of the runs that we did, we managed to learn some things, but it hasn't given me the level of confidence that I would have liked ahead of Australia," he admitted.

"But you have to take the positives out of these difficult situations," he added with trademark optimism.

Kubica's dramatic crash at a low-level rally event in Italy in 2011, as he was coming off a strong Formula One season with Renault, would have been the end of the road for many.

He had multiple fractures to his right elbow, shoulder and leg, and his right forearm was partially severed with his chances of him returning to a normal life, let alone racing again, looking slim.

Kubica has explained in the past that the injury to his arm forced him to adapt the way he drives.

"After my accident, I discovered that to do a roundabout in the road car, you don't have to grab the steering wheel, you can use friction to turn," he said

"F1 is not a road car, but I have been also in school where they give you a bird in the hand and you have to hold it (so) that it doesn't fly away but you cannot hold it too much that it gets scared.

"This is the way you have to hold the steering wheel."

He insists he would not have signed with Williams if not completely sure of being able to withstand the rigours of Formula One, putting himself through demanding training regimes to prepare his body.

Deputy team principal Claire Williams said Kubica earned the right to a seat on merit after spending last season as reserve driver.

"Of course there is a consideration there because you've got to do the right thing from a human perspective, you've got to know that someone is capable of driving one of these machines, not least a team like ours that have lost drivers," she told the official Formula One website.

"So I wanted to make sure I was 100 percent comfortable, and the engineering team were, and every report I had was he is eminently capable of driving an F1 car."

Kubica partners Britain's Formula Two champion George Russell, who will be making his Formula One debut.