We've just seen that at least one Apple Store has sold out of iPhone 5S handsets already.
A recent tweet from Ashleigh Allsopp, a Macaworld writer, shows the store with its sold out sign. Of course this was to be expected when the Apple Stores are the only places you can physically buy the handsets offline.
But if you don't mind buying one on contract and need the 5S handset today, you still have some options. Check out our store buying guide here to see where you can pick one up. But bear in mind if you do want it offline and don't want to wait for the Apple Store, any other network or phone shop will have at least a month before they're allowed to sell SIM-free iPhone 5S models.
But if you're not too bothered about the iPhone 5S specifically why not read our iPhone 5S versus iPhone 5C piece and see if you'd prefer a 5C model, of which there are still plenty available.
UPDATE: Apple Store, Regent Street, will have all three colours in all sizes in stock on Monday. But they warn you should call ahead at 9am for confirmation.