The Apple iPhone will spark the busiest sales day at Carphone Warehouse when it launches in the UK, the firm's boss predicted today.
Chief executive officer Charles Dunstone said the must-have gadget would also mark a turning point in the way UK consumers use their mobile phones.
The iPhone is already on eBay for up to double the £269 price tag it will carry when it launches in the UK at 6.02pm tomorrow.
Mr Dunstone said: "It is a really important day not just for Apple but actually for the phone industry. I think it will move people's perceptions of what a mobile phone is a long way forward."
He predicted Saturday would be the busiest day ever at Carphone Warehouse stores, saying: "It will be the best day we have ever had and our best weekend."
The iPhone goes on sale at Apple, Carphone Warehouse and O2 stores and websites at 6.02pm tomorrow, with stores staying open until about 10pm.
Extra staff have been drafted in to meet high demand and sales of the iPhone will be limited to two products per person.
O2 today shrugged off reports that hackers were preparing to unlock the new iPhone from its network.
The mobile phone giant has an exclusive deal with Apple to run the iPhone on its network. Owners will sign an 18 month contract on tariffs of either £35, £45 or £55 per month.
But about 250,000 of the 1.4 million iPhones sold in the US appear to have been unlocked, according to Apple.
Steve Alder, iPhone director at O2, said: "Why would you want to unlock it? We have the best package of unlimited data and all the benefits of the iPhone. Unlocking it would mean you won't get the full benefit of the iPhone."
Many of the iPhones being sold by UK vendors on the eBay online auction site are described as unlocked, so they can work on any mobile phone network.
Apple vice president of iPod and iPhone product marketing Greg Joswiak: "I think the hacking goes just as a testament to how much people desire this."
The O2 deal gives owners access to an iPhone customer services team and unlimited wi-fi internet access via The Cloud network.
It also gives the user visual voicemail, with the names and numbers of callers who leave messages appearing in an on-screen list.
Unlocking the iPhone also voids the Apple warranty, Mr Alder said.
The iPhone combines a touch-sensitive mobile phone handset with a built-in iPod media player and a wireless internet browser.