Apple today unveiled a major overhaul of its iPhone and iPad operating system based on the vision of its British design chief, Sir Jonathan Ive.

The London-born designer introduced iOS7 at Apple's annual World Wide Developers Conference in San Francisco where he promised the system marked a new "beginning" for the technology giant and would take Apple in an "important new direction".

It came as the firm's CEO Tim Cook revealed the company had sold more than 600 million iOS devices and told his audience that the latest operating system developments were the most significant since the iPhone was launched in 2007.

He said: "The team at Apple has been working incredibly hard on the latest version of iOS and today it is of great thrill that I announce iOS 7.

"iOS7 is the biggest change to iOS since the introduction of the iPhone. It's packed with amazing new features and a stunning new user interface."

The new operating system was showcased in a short video accompanied by an explanation from Sir Jonathan.

The designer, known as Jony, said iOS7 offered a "whole new structure" with a "profound and enduring beauty".

"We see iOS7 as defining an important new direction and in many ways a beginning," he added.

The new operating system arrives just months after Apple posted its first profit slide in a decade and follows tough scrutiny of the firm's tax arrangements on both sides of the Atlantic, along with complaints that the company was failing to innovate.

But experts said today's announcement would go some way to silencing Apple's critics.

Jan Dawson, of research firm Ovum, said: "It should help defuse some of the criticisms about being too staid and not moving quickly enough - on the surface of it, this looks like a major change.

"But I don't think we've seen a really big advance in usability or new features here. Once the keynote buzz quiets, that will become more apparent. And I think some people will never be happy no matter what Apple announces."

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