Apple on Friday launches the iphone, its latest and fastest touch-screen, in 22 countries, including the US and the UK. India will have to wait till September.
Authorities are expecting jammed streets across UK as shoppers flock the 1,250 stores in search of the 3G phone, Apple's combined music player, phone and internet browser.
The mobile phone shop Carphone Warehouse and the network O2, which have exclusive rights to sell the gadget, expect to sell out in nearly all of their shops. Both sold out of their online allocations within hours on Monday, with unexpectedly strong demand crashing 02's website.
Those who buy the phones will find it an expensive experience, as all have to be bought with an accompanying 18-month contract with O2. On the cheapest £30 tariff with the smaller 8GB model, customers will end up paying £639, while on the most expensive £75 tariff, the total bill will be £1,350, with the iPhone 3G thrown in for free.
In coming months, buying an iPhone could be as difficult as purchasing Nintendo's fitness game, Wii Fit, which has been out of stock continuously since its launch in April.
O2 said it would have only a "few dozen" handsets at its 450 shops. After an initial burst of sales, Carphone Warehouse expects the iPhone to be unavailable at many of its 800 shops. Apple will also sell the handset in its 15 British outlets but would not comment on stock levels.
Carphone Warehouse sold out its online allocation of the phones within hours on Monday. On the same day, O2's website crashed after customers made 13,000 "transactional attempts" every second.
"We've never seen any mobile device create the excitement and demand of the iPhone 3G," Ronan Dunne, O2's chief executive, told The Independent.
Announced by Apple's chief executive Steve Jobs in the US last month, the touch-screen iPhone uses the quicker 3G system and has a global positioning system (GPS). Apple says the phone is twice as quick as its forerunner, at half the price.
The company has a target of selling 10 million units worldwide this year. Analysts believe the phone, which automatically switches between Wi-Fi, 3G and EDGE networks to ensure the fastest downloads, will easily pass that figure.