ONE OF THE hallmarks of Tim Cook’s 15-year tenure at the helm of Apple has been an almost metronomic reliability. This may be true even when it comes to succession. On April 20th the iPhone-maker announced that Mr Cook would hand over the CEO role to John Ternus, Apple’s head of hardware engineering (pictured). Few corporate leadership changes are more noteworthy. Yet in late trading, Apple’s shares barely faltered on the news.Mr Ternus, 50, had emerged as the most likely heir-apparent, partly because of his success in revamping the iPhone, and also because he shares some of Mr Cook’s unflashy…