The iPhone, the device that redefined the mobile phone and has helped make Apple the most valuable company in the world, marks its 10th anniversary on Monday.

It was on January 9, 2007, that late Apple founder and chief executive Steve Jobs went on stage at the company's Macworld event to announce the tech giant was to reveal "an iPod, a phone and an internet communicator" - but rather than three separate products being revealed, one of the first truly smart phones was unveiled.

Since then, Apple has sold more than one billion iPhones around the world and has become one of the wealthiest companies.

However, increasing pressure from competitors and the smartphone market beginning to reach saturation point has created new pressures - 2016 has seen sales of the iPhone drop for the first time in the device's history.

Pressure from the likes of Samsung, Google, HTC and Huawei has squeezed the popularity of the iPhone, as has the increase in higher-quality budget and mid-range devices that undercut the iPhone and others on price.

Since the initial announcement in 2007, Apple has introduced 11 new generations of iPhone, drastically redesigning the device on several occasions, as well as altering the screen size and introducing an overall larger version of the phone with the iPhone 6 Plus in 2014, the first iPhone to feature a screen over five inches.

The iPhone also sparked the creation of the App Store, which launched in 2008 and has since been at the heart of the creation of a large number of hugely successful mobile app businesses, including the likes of Angry Birds, Uber and Deliveroo.

Such has been the success of the iPhone that as an individual business the revenue generated by the phone alone has exceeded that of some of its rivals, including Microsoft and Google.

Analysts have referred to the device as a cultural icon and most modern smartphones have been inspired by the iPhone in some form.

The next version of the iPhone, which is expected to be unveiled in September, has already been rumoured to feature a larger screen that covers the majority of the front of the device.