The sleek, touchscreen iPhone has proved so lucrative for Apple that the electronic gadgets manufacturer has unseated Google to become the most valuable company in America's cradle of technological innovation, Silicon Valley.

Queues outside Apple's stores are commonplace since the phone's launch a year ago as shoppers line up to get their hands on the prized device.

On Wall Street, the phenomenal popularity of the phone has fuelled a 44% surge in Apple's share price in 12 months....