The worst-kept secret in Supercars has been confirmed, but it will still be hard to stomach for Ford fans.

Former series champion and 2014 Bathurst winner Mark Winterbottom has confirmed he will switch from Ford to arch rival Holden in 2019 after signing with Charlie Schwerkolt’s Irwin Racing outfit.

Winterbottom, 37, had been linked to a manufacturer move since announcing earlier this month that he would end his 13-year association with Ford powerhouse Tickford Racing.

Yet Blue Oval fans will still find it hard to stomach that Ford poster boy Winterbottom has replaced Lee Holdsworth at Irwin Racing and will link with Holden next year for the first time in his glittering career.

Mark Winterbottom at the Vodafone Gold Coast 600 on the Surfers Paradise street circuit on October 19. Photo: AAP

Winterbottom will contest his last round for Ford in this weekend’s season finale – the Newcastle 500.

“I’m really excited. It was a big call to go … but now I’ve met the team and sponsors and seen what’s coming it’s really exciting,” said Winterbottom.

While some Ford fans will be livid with the switch, Winterbottom reckoned he hadn’t thought much about the ramifications of his dramatic manufacturer switch.

It's confirmed. Team 18 next year sponsored by @IRWINtools I am really excited about what the future holds. Thanks for the opportunity and hopefully you will still support me in 2019. pic.twitter.com/ItiQGwsFGQ

— Mark Winterbottom (@mwinterbottom) November 22, 2018

“I haven’t thought about the badge (constructors’ brand) to be honest.” Winterbottom said.

“I’ve looked at the opportunity, not the brand of car, and haven’t quite come to terms with that at the moment. But from the inside they all look the same and I think the opportunity that Charlie offered was too good to turn down.

“The Holden will be different but, at the same time, if we are winning races I’ll be happy to do it in whatever equipment we have.”

Next year looms as a culture shock for Winterbottom, who moves from the four-car, 60-staff Tickford Racing set-up to the single-vehicle Irwin Racing option that has 12 employees.

“A small team is refreshing. To have the whole team working together for one goal and all working together,” Winterbottom said.

“Every person has to deliver to get the result and that’s myself, the engineers, everyone.

“I’m sure there will be some difficulties like pitstops and data sharing, but in saying that with the weaknesses comes the strengths and having 10 to 12 crew with one goal and having a little family going racing is going to be a great approach.”

-AAP