Apple's iPhone 4 'most successful product' for the business

Demand for Apple's latest smartphone was evident, with queues mounting outside Regent Street's Apple flagship store in the UK on the launch of the highly anticipated iPhone 4, which is 24% thinner than the previous iPhone.

Earlier this month, Apple apologised to customers after its online approval system malfunctioned because of the high level of demand for pre-orders for the new phone. Apple has also said white models of the phone have "proven more challenging to manufacture than expected and, as a result, they will not be available until the second half of July."

The new iPhone 4 includes a five-megapixel camera with LED flash on the back. Using a front-facing camera, the iPhone 4 will also allow users to see their callers and visa versa.

Apple chief executive Steve Jobs said: "This is the most successful product launch in Apple's history. Even so, we apologise to those customers who were turned away because we did not have enough supply."

The phone is currently available in five markets, comprising the US, UK, France, Germany and Japan.