Apple will have been planning this succession for a long time.

Rumours were circulating for a while that 65-year-old Tim Cook was thinking about stepping down, and while a few potential replacements popped up, the name which stuck was the firm's vice president of hardware, 51-year-old John Ternus.

I had an informal meeting with him in the UK recently and I asked him then whether he really was heir apparent to the Apple throne.

He laughed and very smoothly gave me what's known in the newsroom as a "politician's answer" - that is, he didn't actually answer the question at all.

Instead, he enthused about Tim Cook's leadership. But there was no other obvious reason why I was suddenly invited to have coffee with him at that moment, some 25 years after he joined the firm.

I found Ternus polite, friendly, and everything he told me was perfectly delivered, if a bit bland.

I wish I could tell you I got some good gossip, but there wasn't a single unguarded moment. Apple is frustratingly good at curating to the letter what it chooses to say, even in private.

He may have been able to bat off my questions, but Apple - despite its colossal success - faces some serious challenges.

How Ternus responds to them will go a long way to deciding the tech giant's future.

You could say Apple has chosen a replacement for Cook in his own mould: calm, steady, reliable.

While co-founder Steve Jobs was legendary for being brilliant, but also difficult to work with and prone to tantrums, it's hard to imagine either Tim Cook or John Ternus really kicking off. Neither are the kind of fiery characters which currently dominate US public life.

Between them, Cook and Jobs ran the show for around 30 of Apple's 50-year history.

And, despite telling me a few years ago that there was "no good excuse" for the lack of women in the tech sector, Apple - like many big tech firms - is yet to appoint a woman in charge.

John Ternus is affectionately described as "a product guy". He told me he likes to be hands-on with the development teams.

Tim Cook was originally known as "the operations guy" but he also has a very keen interest in hardware.

The first time I met him, he was fascinated by my rather vintage BBC-issued audio recorder, turning it over and over in his hands and admiring the buttons and dials (which I was rather hoping he wouldn't start moving around).

I told him I'd had to borrow some wired headphones from his team as mine had broken, and jokingly expressed surprise that they were still allowed at Apple HQ in the AirPod era. He told me very seriously that they still sold them.

A while later, a member of his team told me Cook was visiting an Apple Store in Europe and saw wired headphones on the wall - and asked his colleague to pass on a message to me that they were still in demand.

It's unfortunate for Cook that his last big product launch, Apple's VR headset, the Vision Pro - which arrived years after VR got going and cost ten times more than its rivals - does not appear to have been a success.

The big challenge for Ternus is AI.

Apple is renowned for moving slowly and strategically - and this has paid vast dividends so far when it comes to its gadgets. The iPhone wasn't the first smartphone on the market when it launched in 2007 but it was the one which redefined the landscape.

At the same time, the company has faced criticism for being slow to jump on soaring AI demand, eventually choosing to incorporate OpenAI's ChatGPT and Google's Gemini technology into its operating systems, unusually choosing partnerships over proprietary AI in this booming area of the industry.

That said, AI is also still proving quite hit and miss despite all the hype, with reports of disappointing adoption rates among businesses and mutterings that it has been over-sold.

"Apple hasn't thrown the kitchen sink at AI opportunities," comments Susannah Streeter, chief investment strategist at Wealth Club.

"There's an expectation that John Ternus will continue this defensive strategy, without over-deploying capital, which seems sensible given concerns about an AI bubble potentially bursting."

Don't mention that to the other tech giants, who have very much thrown the kitchen sink and everything else at AI.

One of the next stages in the broader AI landscape is its physical embodiment - essentially meaning robots.

Should Ternus be thinking about Apple's next big unveiling being a humanoid? Can the firm make that pivot from small screen to large bot?

Apple's personal consumer products are renowned for their small, sleek design, but AI doesn't have to look and feel nice in your hands. It needs to work.

There's another more diplomatic challenge which Ternus will have to navigate: how to get on with a US president who is notoriously fickle.

Tim Cook has made a point of describing himself as politically neutral. He did, however, donate to Donald Trump's inauguration fund and he also gave him a rather elaborate statue with a 24 karat gold base as a gift.

Apple still got knocked about in Trump's tariff frenzy though, because despite moving manufacturing away from China where it can, it hasn't been able to completely disentangle itself completely from the production powerhouse of the east.

But in a long social media post on Tuesday, Trump wrote that he had "always been a big fan of Tim Cook" and that Cook would occasionally call him to ask for help on issues relating to the business.

He ended it by saying: "Quite simply, Tim Cook is an incredible guy!!!"

Finally, in an age of personality power, it will be interesting to see how much of his private life the former swimming champion John Ternus is willing to share.

Cook announced he was gay in 2014 but other than that he has never shared much about his life outside of work.

I suspect Apple is his life, inside and outside of work. He once admitted to me that he was "not much of a role model" for work-life balance.

Cook always chose to pre-record his big announcements, and while Jobs leapt around on stage, Cook's delivery style was probably more pitch-perfect, but also less passionate.

Ternus will have to decide whether to open up more in an authenticity-hungry culture where we want to see the world's most powerful figures being themselves - or at least doing a good job of playing the part.

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