Although the Spaniard’s first experience at Indianapolis was a private test arranged by McLaren-Honda-Andretti, the circuit pulled out all the stops with a proper broadcast of the event involving a studio, in-depth interviews and fly-on-the-wall access.

The test was broadcast live on digital platforms YouTube and Facebook, and generated an unprecedented level of interest.

Reaching peaks of more than 70,000 concurrent viewers at times, the official figures recorded by YouTube and Facebook showed a combined overall viewership of 2,149,000 views.

This was split up between 950,000 views on IndyCar’s official Facebook channel and 1.2 million viewers on the official IndyCar channel on YouTube.

It was also was one of YouTube's top 10 trending videos of the day.

Lessons for F1

These numbers are in excess of what many popular categories – like F1 and MotoGP – get for race highlights and incidents, and proves that Alonso’s IndyCar effort has captured the imagination of fans.

What makes the viewership even more remarkable is that this was just a single-car test, and took place in the middle of the week.

It has already prompted suggestions that F1 could learn lessons from what has happened – with the Alonso coverage delivering remarkable access to his conversations with engineers, his run programme and emotions as he built up his speed.

F1 broadcaster Sky Sports aired a pre-season Barcelona test live back in 2013, but the effort was not repeated because the expense of doing so outweighed the level of interest from fans.

However, in F1 testing, cars are kept hidden behind screens and camera crews are given very limited access to drivers and engineers, so are unable to generate the kind of interest that IndyCar was able to do with Alonso on Wednesday.