McLaren regard the 18-year-old as a special talent who was too good to ignore.

Even when urging patience next season with the teenager, McLaren boss Zak Brown couldn’t disguise his enthusiasm for a driver who has excelled in every series of his nascent career to date.

“He’s an immense talent,” Brown said. “In all the junior formula, he has been dominant and we are convinced he is a star of the future.”

The weakness of Norris’ candidature is his age – especially when tallied with the 24-year-old Carlos Sainz. But Brown’s says the line-up – likely to be the youngest on the grid next season – is the right fit for McLaren’s current position.

“We are in rebuilding mode, and to have two extremely quick young drivers, one with a decent amount of experience along with one who is inexperienced is a good combination for us when we are rebuilding and looking out over a five-year horizon,” he explained.

“We pretty easily came to the conclusion that Lando was the driver we wanted.”

How important were Norris’ trial runs in the McLaren?
Norris has tested on four occasions for McLaren, most recently in last month’s two-dayer after the Hungarian GP, and drove in Practice One at the Belgian and Italian GPs.

“I knew that if l was to prove I was worth it, I had to do well,” said Norris at a press briefing on Tuesday. His suspicion was right: although it wasn’t acknowledged at the time, these outings were his final auditions for the 2019 seat.

“He did extremely well,” said Brown. “It was his final test, if you want to call it that. It was less about speed and more about how he would take to the environment with the big boys.”

Maybe so, but Norris’ speed in both P1 outings was hugely impressive.

At Spa, he was quicker than Stoffel Vandoorne, although he then finished half a second down on Alonso at a rain-hit Monza last Friday. But the timesheet didn’t tell the full story. “He and Fernando were trading fastest times in difficult weather conditions and then on Lando’s last run he was up two tenths on his first sector but he had to abort that lap,” recounted Brown. “I think he would have ended there or thereabouts – a tenth up, a tenth slower.”

McLaren had seen enough. The decision to appoint Norris was rubber-stamped over the next 48 hours and, to the youngster’s surprise, he was informed of his promotion to a full 2019 seat on Sunday morning.

Why has Vandoorne been dropped?
Vandoorne has disappointed since replacing Jenson Button two seasons ago and his record this year is dismal: out-qualified by Alonso in every grand prix, out-scored by 8 points to 44. But the team’s belief in Vandoorne’s quality seems genuine and they have repeatedly highlighted statistical evidence he has been closer to Alonso than a lot of the Spaniard’s previous team-mates.

The bottom line, however, is that McLaren believe Norris is the better driver – and, with Vandoorne eight years older, the better bet for the future.

“Ultimately we look to the future and feel Lando’s a future star,” said Brown.

Vandoorne’s fate was sealed on F1’s first day back from its summer holidays when Norris, on his F1 weekend debut, out-paced the Belgian in Friday practice at Spa.

Even with McLaren making allowances for the disruption Vandoorne suffered during the session, it was a hinge moment in their decision making.