Apple CEO Tim Cook once called himself the 'Attila the Hun of inventory'

Tim Cook has taken to Apple to record-breaking heights with a smile on his face - but behind that cheerful demeanour is an iron will and a relentless focus.

A recent note to investors from UBS has the perfect example of this: Before being poached by then-CEO Steve Jobs, Cook worked as VP for Corporate Materials at Compaq. And while there, he gave himself a nickname: "Attila the Hun of inventory."

Attila the Hun was a feared 5th century AD ruler of the vast Hunnic Empire, and the scourge of the Eastern Roman Empire.

Tim Cook is a 54-year-old Alabama native and hiking enthusiast.

After being brought on as head of Operations, Cook made sure he lived up to his self-bequeathed title. "Apple under Jobs was a roller coaster, but Cook's operations fief was orderly and disciplined, the Wall Street Journal wrote last year, with meetings often lasting hours and going into gruelling detail. "Your numbers," he once told one planner, "make me want to jump out that window over there."

Cook is a "tough cookie," UBS says, "and has been a tough negotiator in creating arguably the world's best-run supply chain."