"I have some very sad news to share with all of you. Steve passed away earlier today." So begins Tim Cook’s email to Apple employees. "Apple has lost a visionary and creative genius, and the world has lost an amazing human being. Those of us who have been fortunate enough to know and work with Steve have lost a dear friend and an inspiring mentor."

Apple Steve Jobs
The image on Apple’s homepage

It was the email Cook must have been expecting to write for a while. Jobs’ death at the age of 56 was not unexpected – the man behind the iPhone, iPad, and iPod had been suffering from cancer for a number of years and was on his third stint of medical leave from Cupertino when he stepped down as CEO in August this year.

But that’s not to say his death is any less shocking or upsetting, as the outpouring of grief from not only the technology industry but the wider world shows. "For those of us lucky enough to get to work with Steve, it’s been an insanely great honour. I will miss Steve immensely," said Bill Gates, Microsoft founder and one of Jobs’ great rivals.

"Steve, thank you for being a mentor and a friend. Thanks for showing that what you build can change the world. I will miss you," added Facebook founder Mark Zuckerberg.

"Steve was among the greatest of American innovators – brave enough to think differently, bold enough to believe he could change the world, and talented enough to do it," said US president Barack Obama.

Cook was the one who stepped into Jobs’ shoes when he was on medical leave and was Jobs’ choice to replace him as CEO. It is safe to assume succession planning has been going on for a while.

As was discussed at length when that news was announced in the short-term Apple is in safe hands. Its product roadmap is established for the next few years and as Cook points out in his email: "Steve leaves behind a company that only he could have built, and his spirit will forever be the foundation of Apple."

But beyond that? Fortune retold a tale of Jobs’ reaction to the critical panning handed out to MobileMe, particularly from The Wall Street Journal’s Walt Mossberg, a long time Apple watcher.

According to Fortune: "Jobs walked in, clad in his trademark black mock turtleneck and blue jeans, clasped his hands together, and asked a simple question: ‘Can anyone tell me what MobileMe is supposed to do?’ Having received a satisfactory answer, he continued, ‘So why the fuck doesn’t it do that?’"

He then tore into the group, accusing them of "tarnishing" Apple’s reputation and replacing the executive in charge of the group there and then.

Does Apple veteran Cook have that in his locker? His performance at the unveiling of the iPhone 4S didn’t give much away as he left most of the talking to Apple’s marketing boss Phil Schiller.

The reaction to the phone was underwhelming – most observers had been expecting a brand new iPhone 5 rather than just an updated version of a device that was released well over a year ago, making it an old man in the fast moving world of smartphones.

That of course was not Cook’s fault, the development for the iPhone 4S would have begun a long time ago. But as Silicon Valley analyst Rob Enderle pointed out (before Jobs’ death was announced): "With Jobs there you would have walked away thinking the iPhone 4S was better than it was. But, in this case people walked away thinking it was less than what it was."

Jobs’ genius was in making beautiful products that were easy to use and that people wanted to buy, products that fundamentally and forever changed the way millions of people the world over use technology and consume films, music and countless other forms of content. That is now ingrained in the Apple psyche and is a trait that the firm will not lose any time soon.

Jobs is irreplaceable, a one-off. Of that there is no doubt. But that doesn’t mean panic should set in at Apple… or amongst its shareholders. Gartner analyst Michael Gartenberg agrees: "Tim Cook and his stellar management team will succeed Steve and the company will grow and prosper. They will not, however, replace him," he wrote on Twitter.

As Cook’s email concludes: "No words can adequately express our sadness at Steve’s death or our gratitude for the opportunity to work with him. We will honour his memory by dedicating ourselves to continuing the work he loved so much."