Toto Wolff has revealed Christian Horner initially refused to sign a document backing his wife Susie in her fight against the FIA.

In her role as F1 Academy managing director, Mrs Wolff was falsely accused of overstepping the mark when it came to sharing information with her husband, Mercedes team principal Mr Wolff.

The FIA launched an investigation into a potential conflict of interest but called a halt after the Wolffs launched a fierce denial in response.

All 10 F1 bosses gave their support to her in a signed letter, but Mercedes supremo Wolff revealed Horner initially resisted before signing.

“The response was great. I didn’t make a single phone call to any team. Fred [Vasseur, Ferarri boss] took it into his hands and said: ‘This is just so unfair’. From Guenther Steiner [former Haas team principal] to James Vowles [Williams boss], everybody jumped onto this.

“They were all ready, but for Christian, to sign a document in our support. As far as I understand it he said: ‘I’m having my own Sky interview and I’m going to say I’m not part of it. I’m not signing the document.’ The other nine teams said: ‘Fine.’

“But obviously he was advised that wouldn’t look great and he should be part of the statement. In the second iteration, he tried to get the word ‘official’ in the statement. He wanted a note to say that no one [among the team principals] officially complained to the FIA.

“The other teams said: ‘Fine. We do our declaration and you do your own.’ At the end, he signed it.”