Steve Jobs penned a note to the world explaining his absence from his usual Macworld keynote speech and then a week later announced he was taking a six-month leave of absence on health grounds.

The 53-year-old Apple chief executive, who has noticeably lost weight but previously declined to comment about rumours over illness, first wrote to the Apple community: “Unfortunately, my decision to have Phil [Schiller, senior vice-president of worldwide product marketing] deliver the Macworld keynote set off another flurry of rumours about my health, with some even publishing stories of me on my deathbed.”