Mercedes enjoyed their best race weekend of F1 2023 in Barcelona, picking up their first double-podium finish of the year.

Lewis Hamilton still finished over 24 seconds behind race winner Max Verstappen, who maintained Red Bull’s incredible record of winning every race so far.

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Speaking after the race, Horner was asked about Mercedes’ improved form.

“For sure they’ve made a step,” Horner said. “They’ve introduced pretty much a B-spec car.

“They must have used a significant proportion of their development budget on that. And when I look at the gap at the end of the race it’s very similar to where it was in Bahrain. All that’s happening is the running order behind us seems to vary from race to race.

“Fernando [Alonso] last weekend, Mercedes this weekend and it’ll be interesting to see how that plays out over the next few races.”

Red Bull’s rapid development is likely to be put on hold due to restrictions over the amount of aerodynamic testing they can do following their breach of the 2021 cost cap.

“We’re strategically using the ATR because of course we have to balance it for this year and for next year with the development that is currently going on,” Horner explained.

“So the team are just doing an incredible job being extremely efficient. You can see we’ve very subtly developed the car since since Bahrain. We’ve seen others bring in significant upgrades now and the margin has remained pretty much the same from where it was in Bahrain. 

“That’s hugely encouraging to everybody in Milton Keynes, who is doing an outstanding job at the moment.”