Lewis Hamilton has stood up for rookie Lance Stroll

Stroll, the 18-year-old who will become only the second youngest driver to start a grand prix when the lights go out in Melbourne next month, has endured a troubled start to his new career.

The Canadian, whose rise in motorsport has been bankrolled by his billionaire father Lawrence Stroll, lasted only 12 laps in his first meaningful F1 running following a spin on Tuesday.

He was then involved in two further incidents on his return to the Williams cockpit 24 hours later, the last of which seeing him sustain significant damage to the front of his car.

While Stroll completed nearly a century of laps in between his accidents, his age and inexperience could be cause for concern ahead of the new season.

The cars this year are set to be the fastest ever seen in the sport following a radical overhaul of the way in which they are designed.

But Hamilton, who suffered a memorable high-speed crash in pre-season testing before his debut back in 2007, expressed sympathy for the teenager.

"I feel for him in the sense that it is the toughest year to come into Formula One, being that these are the fastest and most physical cars," said the 32-year-old.

"It is to be expected because it is not an easy car to drive at all. It is so much faster and precision is even more important than the past. Last year's car is easy compared to this year's.

"These are only the first days and you cannot jump in and drive from no experience at all to being consistent. It is actually good for him to go through this now rather than at the first race."

Stroll will have two more days in next week's final test to get to grips with the sport before the season gets under way in Melbourne on March 26.

And it will be Hamilton's Mercedes team who are likely to travel to Australia as the overwhelming favourites to build on their dominance of the sport following a sterling week in Spain.

Valtteri Bottas, fastest on Wednesday, and Hamilton completed a mammoth 170 laps as Mercedes continued to rack up the mileage. World champion Nico Rosberg was also at the Circuit de Catalunya to observe proceedings as a fan.

"It's been a great test so far for the team," Hamilton added. "It's unreal. I'm like a kid on a roller coaster ride because it is so much better than it was before.

"This is definitely the fastest I've ever driven in F1. It feels amazing and I hope it separates the men from the boys."

Ferrari appear to be the closest challengers to Mercedes at this stage. Sebastian Vettel, the four-time champion, turned in 139 laps - more than two race distances of this circuit - and was only marginally slower than Bottas' best lap.

British team McLaren have suffered a difficult week with their hapless Honda engine suffering a host of reliability issues.

But double world champion Fernando Alonso was back in the car on Wednesday and managed to get 72 laps under his belt. The Spaniard, however, was nearly three seconds off Bottas.