The Williams F1 team has revealed why they opted to choose rookie driver Sergey Sirotkin to take over from Felipe Massa in 2018.
Williams chief executive officer Mike O’Driscoll said that it had come down to Sirotkin's performance in post-season testing at Abu Dhabi at the start of December.
O’Driscoll said that Sirotkin had been "flawless" in the car, a comment that was endorsed by the team's chief technical officer Paddy Lowe.
“What was obvious was how calm Sergey was in this moment, when he realised he needed to perform,” Lowe explained at a Williams-SMP Racing joint event in Moscow.
“From the first few laps that he did in the car, you could feel the atmosphere in the garage," he continued. "The engineers - how immediately they were impressed with his times, his feedback, with his precision.
“He made no mistakes," Lowe added. "The feeling that he was a great driver was there very early on.
"It really was a universal feeling among the engineers that this was the guy we needed in the car."
Several drivers were believed to be in contention to replace Massa.
Paul di Resta, Pascal Wehrlein and Daniil Kvyat were all believed to be in the running. But the favourite to get the spot was former Sauber and Renault driver Robert Kubica.
Williams did not disclose details of how the test went. However it's believed that Kubica wasn't as fast as they had hoped, while Sirotkin exceeded expectations.
SMP Racing, which is backing Sirotkin's Formula 1 bid, said it had gone in to the post-season test determined to show what the 22-year-old Russian could do in the car.
"We were intentionally targeting, and preparing for, the Abu Dhabi test,” said SMP Racing chief executive Dmitry Samorukov.
“We understood that Williams was going to be one of the best options.
“It's definitely not just that Sergey showed up, set a good time, they spotted him and now he has the seat," he added. "That was more the culmination of the work done up to that point."
Williams has rebuffed suggestions that Sirotkin's signing is financially motivated. The team revealed this week that they had a multi-year option on the driver's services.
“We’re very excited about what Sergey can do this year, and even in the many years ahead," said Lowe.