We may have two new players entering the 4G market from today, with new networks from Vodafone and O2 launching alongside the already established EE, but Three is aiming to gazump them all by making a hugely bold announcement itself. If you're a Three customer with a 4G-ready phone you will be upgraded to 4G speeds for free this December.

Initially starting in London, Birmingham and Manchester, the coverage should grow to 50 cities by the end of 2014. Three then promises that there will be 98 per cent coverage by the end of 2015.

It will be tough for Three to compete against its main rivals, with EE in 105 towns now, and O2 and Vodafone to be available in 13 and 12 cities respectively by the end of the year, but the network has an ace up its sleeve.

Not only will it not be raising prices for existing customers, but those on all-you-can-eat data plans will also continue to receive unlimited data, but at greater speeds than even the existing "Ultrafast" internet connectivity Three currently offers.

The network will also provide the changeover with a simple software update. Those with 4G-capable phones just need to install the update to enjoy 4G speed.

For new customers, prices for 4G-ready phones on Three tariffs will cost from £32 a month on a contract with a HTC One for a £29 up-front cost. That also includes 500 minutes of talk time, 5,000 texts and, of course, that all-you-can-eat data.

Other handsets are available too, including the Samsung Galaxy S4 on the same contract, but at £33 a month with no up-front fee.

Three's best 4G-ready deal is £20 per month for a Huawei Ascend P2. That also come with all-you-can-eat data which will be shifted to 4G when it becomes available.