hristian Horner should be in steamy Singapore, preparing for another grand prix victory, but here he is, at home on an autumnal morning in genteel Highgate as his wife, Geri Halliwell-Horner, welcomes me with a cheerful hug. Horner smiles as the former Spice Girl produces an impressive imitation of my South African accent which echoes her old headteacher at Watford Girls.

After the most controversial man in the recent history of Formula One says hello, Halliwell-Horner and I discuss the fact that my two daughters also went to her school and that one of their history textbooks had her name printed on the inside page – while the ex-Ginger Spice talks about gritty old Watford, grammar school education and Nelson Mandela.

I joke that it feels like I'm interviewing Halliwell-Horner instead of Horner. Everyone laughs but I will soon ask Horner about the impact on his marriage in 2024 when an investigation was carried out into allegations he had sent "hundreds" of inappropriate texts and photographs to a female employee when Red Bull's team principal. The woman was apparently "upset, angry, scared, intimidated and lonely" while the tabloids speculated that Halliwell-Horner was "furious".

Horner was exonerated by two independent investigations but other hurtful circumstances then surrounded his sudden departure from Red Bull in July 2025. The team has struggled since then but, nine days ago, at the Bahrain Grand Prix, Max Verstappen won Red Bull's first race with an engine built entirely by the team. Verstappen then won again in Singapore this past Sunday. That feat of engineering had been conceived and instigated by Horner near the end of his remarkable 20 years at Red Bull.

When Halliwell-Horner disappears after a final hug, Horner is amiable yet careful. However, the 52-year-old admits his distress after he was forced out: "It felt particularly brutal and sad to finish in that manner. But I now have a reasonable relationship with Oliver Mintzlaff [the CEO of corporate projects at Red Bull]. He rang the other day and thanked me for all I'd done for the engine."

His dismissal, Horner reiterates, "was painful. Very painful. I didn't really process it till a month later because, in the immediate aftermath, I focused on supporting my daughter [Olivia] through a hideous period."

Horner and his former partner, Beverley Allen, became parents to Olivia in 2013. After they separated, he and Allen remained on good terms and so grief, following her death from eye cancer, framed his demise at Red Bull. As he recalls that difficult period, he pays fleeting tribute to his arch-rival, Toto Wolff, the head of Mercedes, who has addressed his battle with depression.

"Toto was very brave to talk openly about such a factor for people our age. I hadn't experienced those issues but I had an appreciation during this period of how people could [suffer]. The identity of many middle-aged guys is through their work. Suddenly you have that stripped and taken from you. Who are you? What are you? What is your purpose? You either curl up into a ball or brush yourself down and get up."

Horner, who arrived in 2005 as the youngest team principal in F1 history, adds: "When I started at Red Bull, there were under 400 people. When I left, there was 2,200. I poured my heart and soul into that business and convinced people to leave other teams for Red Bull. I never had a big turnover in staff because there was tremendous loyalty over a long period. The startup engine business had been founded in 2021 and I was about to get it on the track when I left. I felt great sadness in not seeing that engine in a car."

He broke down briefly while telling staff of his fate. "It was very strange because that group became your extended family. So the tears on grown men's faces was deeply moving."

In his new book, which provides a thorough overview of his career, Horner describes the day he replaced Tony Purnell, his predecessor, in 2005: "Formula One is ruthless, I thought, watching from my car as Tony and Dave Pitchforth, their just-fired managing director, carried glum expressions and cardboard boxes stuffed with personal belongings … when I was eventually shown to my office, it resembled a crime scene. A barely drunk cup of coffee had been abandoned on the desk. Through the walls, I heard Tony's PA sobbing."

Horner says now: "History repeats itself. Not all teams act in that way. A lot of teams haven't delivered over the years but you don't see the same brutality as when I left. We had pole position at the previous race."

At last year's British Grand Prix, just before Horner's sacking, Verstappen was leading when "the rain came".

Horner also mentions his "relief" at leaving. "The last two years had been pretty tough but it was a particularly sensitive time, with the bereavement of my daughter's mum the previous week. I had an 11-year-old child grieving her mother. Nothing was more important than that."

There had been a power struggle at Red Bull following the death in 2022 of Dietrich Mateschitz, the company's billionaire founder who always backed Horner. Both Helmut Marko, a key consultant, and Jos Verstappen, Max's father, seemed keen to undermine Horner. "Helmut could be blunt and I was disappointed he'd stayed as a guest of our family two days before [Horner's sacking] with no indication this was coming," Horner reveals.

What about Verstappen Sr? "There's nothing to say."

Were the Verstappens partly responsible for Horner's removal? "No, it was a Red Bull decision. After Dietrich died, things changed in the leadership."

Horner says the reasons for his sacking remain opaque, apart from a general discontent that the team no longer matched the domination it had enjoyed in two separate spells when Sebastian Vettel and Verstappen won multiple championships: "I think it was a feeling there was too much control in my hands. But I wasn't really given a reason."

Did the 2024 allegations contribute to his dismissal? "I'd come through that, dismissed them. So this was more focused on performance and the future."

Was he worried his marriage might be in jeopardy after the texts and photographs were leaked? "My wife was a pillar of support throughout and I just had to believe in the process. I've said enough about it in the book and previously."

Yet the book does not outline the allegations against him or provide any details of his defence. "I've said everything I can say, and there are certain legal reasons [why] I'm not at liberty to go further."

Horner is more precise when asked if there is a chance he might never work in F1 again. "Absolutely. But if I don't go back I had a hell of a run. I won one in every four races I competed in. I had 287 podiums out of 405 races."

He says: "Nobody could take away the 124 wins and 14 championships [six constructors' and eight drivers' titles]. But I felt particularly hurt and robbed I didn't have the opportunity to see that [Red Bull-manufactured] Powertrains engine win."

Horner watched Verstappen's victory the Sunday before last on television and "I felt very proud seeing what it meant to everybody and that they sent the Powertrains representative on to the podium. I had messages throughout the team and I texted Max after the race. He was very magnanimous and it was a landmark moment to see that engine win. It reinforced to me that, if you assemble the right people with the right culture and the necessary tools, anything is possible."

Yet he still believes the team has lost its mojo. "Red Bull has been the maverick team. It's pushed the boundaries. Only Red Bull would do something crazy enough to build a new engine as a subsidiary of a fizzy drinks manufacturer. Its mantra was to be nonconformist, to be a disruptor. It's a little different now."

Who is in charge of Red Bull's team – Laurent Mekies, his successor, or Max Verstappen? He laughs. "I'm not getting drawn into that. Ultimately Oliver Mintzlaff is the most senior guy and obviously Max is a massive asset. I employed Laurent but I can't judge how he operates."

Horner argues that his comments last month about Ferrari being "a dream job" applied more to other people than himself. He would prefer to return with a team where he has a part-ownership stake. In regard to Ferrari and their currently beleaguered team principal, Horner suggests "Fred Vasseur is an experienced guy. He's done a decent job. But I, more than anyone, know the pressures of running a competitive organisation. My comments got taken out of context.

"Ferrari is the biggest brand in F1. It's the most historic team. But I've accumulated some phenomenal capital behind me, to look at the next move I potentially make in the sport. That would be with ownership attached to it and Ferrari aren't going to sell shares. So I'm happy to sit outside the sport and see what opportunities present themselves over the coming months or years. It's not a prerequisite that I go back. I would only return for the right opportunity with like-minded people that want to win. I would never go back just to take part."

Horner says: "For the last 21 years I would have been sitting in Singapore right now. But it's my daughter's 13th birthday today and I'm taking her to see Hamilton at the theatre tonight."

What does he miss most about F1? "The people, the team, the competition. I still love the sport but I don't miss the travel and politics."

Wolff said Horner had "broken too much glass" to return to F1. Horner grins: "He also said this [Red Bull] engine was going to be completely shit and a disaster. Toto's got it quite easy at the moment. Zak Brown [the head of McLaren] is compromised because he's using Toto's engine so he can't ruffle feathers. All sport needs rivalry, whether it's Ferguson and Wenger, Mourinho and Guardiola. It percolates and polarises. I used that to galvanise good people to take on Mercedes."

Yet F1 takes its toll and Horner admits he has suffered panic attacks. "I didn't know what it was. You suddenly feel dizzy and conscious of your breathing and you think there's something strange going on. I put it down to having had too much coffee on an oppressive, muggy, thundery day. Then it happened again. I got checked out and there was nothing physically the matter. They said: 'We think you have anxiety. Your breathing's very shallow.' It was my body telling me you're pushing pretty hard here. I'm able to recognise the symptoms now and let it go, and breathe."

What might he be doing 10 years from now? "I'm looking forward to finding out. It could be at a racetrack, it could be sitting on a tractor."

He laughs again before showing his real conviction. "I know my strength is getting a group of people across different skill sets to work as a team. That's possibly applicable to other things but, at the moment, the only thing that really motivates and excites me is Formula One."

Drive by Christian Horner is published by Bantam on 22 October. Available on pre-order from Guardian Bookshop. He will be sharing stories from the book on tour across the UK from 17-26 October.