Alonso completes opening phases of Indy ROP test

The start of the eagerly-awaited test was delayed as cold temperatures meant Andretti Autosport regular Marco Andretti could not shake down Alonso's car as early as the team had intended.

Once Andretti had carried out several runs to prepare the car's set-up, he discussed the car and track conditions with Alonso before the double Formula 1 champion set off for his first exploratory laps of the oval just before 11am local time.

Alonso proceeded to complete the first two phases of Rookie Orientation Practice, with a best lap of 213.852mph.

Andretti explained his aim had been to "just get a conservative balance".

"At this place understeer's not good either, so you just need to make sure it's stuck so he can get confidence. It's pretty good," said Andretti.

"With this level of downforce - it's like race downforce - when there's no traffic and you're by yourself, it's just stuck. That's what you want for the first run."

McLaren CEO Zak Brown said Alonso was "very excited" but was taking his preparations extremely seriously.

"This is so cool. I feel like a fan and I think we're all super-excited," said Brown. "Fernando is very excited. He's like a little kid. You should see his texts to me.

"He's probably watched 25 Indy 500s. He's watched Ed Carpenter's entire race from an in-car camera. I've never seen him so happy."

Rookie Orientation Practice consists of drivers running at steadily-increased prescribed speeds to acclimatise to the track before being allowed to run flat out.

Among the people in attendance at Indianapolis was Johnny Rutherford, who won the 500 with McLaren in 1974 and '76 when it ran a major IndyCar effort alongside its F1 programme.

"I think he'll remember this for the rest of his life," Rutherford said of Alonso's first taste of Indy. "Your rookie year is etched into your mind. This is the big place.

"If they had told me after my first lap around here 'alright kid, that's it, you've got to go home', I'd have been happy to have done that."

He emphasised that Alonso would need to be cautious on his first day.

"You don't want to go out there and set the world on fire," Rutherford added. "You want to sneak up on it. If you try to do it all at once, you're in trouble."

After the initial test day, Alonso will not be back in the IndyCar until official Indy 500 practice begins on Monday May 15 - the day after he contests F1's Spanish Grand Prix with McLaren.