The white, yet to be launched white version of the iPhone has spotted in London by a crew from Sky News, in the Apple store in Regent street itself on the day of launch.
We didn't see any white iPhones on display or on sale while we were queuing up fo several hours on the 24th but some units might have slipped over the counter.
Ironically, Apple said a few days ago that the phone won't be available until the second half of July 2010. Apple did not say what the challenges are and to the novice, swapping a colour for another shouldn't make any differences.
Unexpectedly demand for the colour was so high however that it compelled the company to release a statement. The iPhone is still unavailable for preorder even on Apple's website while the black model has a delivery window of three weeks approximately.
Slate (opens in new tab) posits that changing from black to white is not simply a matter of changing colours. The old iPhone 3GS was affected by complaints about discolouration due to overheating. It is however more likely that this is due to the higher than expected demand for this particular colour.
A quick look at Google Trends (opens in new tab) show that search for the white iPhone 4 is several times higher than that of its black counterpart and this is particularly true in the US and in the UK.