Ten years ago, on this very day, the Mercedes-AMG-Petronas F1 team recorded its first race win in 57 years and the rest, as we all know, is history.
The behaviour of the Aston Martin driver, who was accused of weaving around the track, did not sit well with the Finn.
The 32-year-old Finnish driver joined Alfa Romeo this season from Mercedes and has had a strong start to the campaign so far.
The Albert Park track has undergone a number of changes since the last time Formula One cars zoomed on its asphalt.
Mercedes, who had won the previous eight Constructors' Championships, is now scraping for whatever points they can.
On the soft compound tyres, Leclerc, who didn't break cover until halfway through the session, set a time of 1m 30.772s in the closing stages.
Due to a late red flag caused by Valterri Bottas's stoppage, Max Verstappen only had 20 minutes for a final time attack.
The Alfa Romeo F1 team, which will be led by Valtteri Bottas and Zhou Guanyu, continued its expansion towards decentralised finance.
The Finn completed only 10 laps in the Alfa Romeo C42, the least of any driver on the day, as his team struggled with reliability issues.
Alfa Romeo became the final team to reveal their challenger's livery for the season, which they described to be a subtle nod to the past.