ARM: Britain's most successful tech company you've never heard of

Without ARM, the iPhone and other smartphones wouldn't work. Hardly anyone knows it - and that's just how Cambridge's 'Silicon Fen' company likes it

In a loose collection of offices on an underwhelming business park outside of Cambridge sits Britain's most successful technology company, ARM. You've probably never heard of it, but ARM's designs are at the heart of the iPhone and nearly every other modern smartphone. It has fingers in almost every other area of technology, from fitness trackers to server farms. It records profit margins that analysts have described as "impossible" (in a good way), and goes a long way to helping justify the "Silicon Fen" label sometimes applied to Cambridge's tech scene. So how did one company get so successful without anyone really noticing? And, more importantly, what does ARM actually do?