He was one of two F1 stars to sample a Supercar, with Sergio Perez also driving a Red Bull-backed Triple Eight Commodore.
For the Alonso drive, Randle rode shotgun to help give the Spaniard some tips on how to drive the car.
An attempt to link the two via radio wasn't overly successful, so Randle had to revert to using hand signals to tell Alonso what gear he should be in for each corner.
"The radio worked but it wasn’t that great, I couldn’t really hear him, and I don’t think he could really hear me," Randle told the Castrol Motorsport News podcast. "So it was just easier to do the third gear, fourth gear, second gear [hand signals]. He knew straight away what it meant.
"There were a couple of times he was on his way into the corner and I just said ‘down one more gear’ and he’d give me a thumbs up.
"Then he remembered the gears after that and he was fine. For example Turn 9 and 10 is third gear for us and seventh gear for them, I don’t think he was expecting that to be third gear!"
After the laps with Randle in the passenger seat Alonso returned to the track for a second run with his Alpine race engineer Karel Loos in the passenger seat.
While Perez drove Triple Eight's spare chassis, Alonso was actually in Randle's race car for his demo laps.
Randle admits that made him a little nervous, particularly as both Formula 1 drivers were reluctant to right foot brake, which is better suited to the Supercars braking and downshifting procedure.
As it turned out the only issue was a brief off at Turn 1 towards the end of the run.
"A little bit, knowing that he wasn’t right-foot braking with the clutch," said Randle when asked is he was worried about his car.
"The downshifts were very spaced out and the upshifts he was nailing it. He got on top of it pretty quickly.
"But he was definitely holding back, and with a passenger, it was definitely low-risk."
It was later revealed that Perez wasn't as kind on the downshifts in the T8 car with the V8 motor hitting around 8800 rpm with some of the more aggressive blips of the throttle.
The demonstration was a well-kept secret until the Thursday morning when the news was broken by Motorsport.com.
According to Randle it wasn't a secret they needed to keep for long, the entire Alonso deal coming together in around a week.
"Early last week I was at a Castrol conference up on the Gold Coast and they mentioned that they were trying to tee something up with Fernando, just a face-to-face Q&A kind of thing," he said.
"I know the girl who runs the PR for Alpine, Alex Thomson, I sent her a message and said we were trying to do something there and it’d be cool if we could organise a hot lap or something, just throwing a thought out which I thought would be shut down pretty quickly.
"I think she passed it on to more people internally at Alpine. It got back to Castrol and, I don’t know the complete details, but [Tickford PR] Mitch Robinson had to do his handy work as well, everyone had a role to play in it happening, and I think it was one of the best PR things they’ve done in such a short period of time.
"These things can take four, six, eight weeks to plan and it was pretty cool that we pulled it off in about a week."
