TECH WEEKLY: The development that has reappeared after a 25-year absence – but what benefit does it bring?

In a little-observed development back at Monza in September, we saw the first reappearance of the brake disc groove after a quarter-century absence. This was on the Carbone Industrie brake discs supplied to the Williams team.

Since then, Alpine has also raced them, running them for the first time in Mexico. Carbone Industrie supplies six of the 10 teams with discs so we may be seeing the feature appear on other cars subsequently.

But what is the significance of the four grooves, cut diagonally into the carbon fibre discs?