The UK's biggest mobile service provider by customer base, with over 27 million users, has rebranded as EE to offer the 4G 'long term evolution' (LTE) services to customers, capable of delivering mobile broadband speeds of 100Mbps using more efficient frequencies.
Long established in countries such as America, Canada and Japan, fourth-generation mobile is now live in four major cities - London, Birmingham, Cardiff, and Bristol. The network will reach 16 locations in total by the end of the year, covering 20m people.
EE branding will hit the high street in the coming weeks, taking over old Orange and T-Mobile stores, and offering new 4G tariffs and smartphones that can receive the frequency, including models from Samsung and Nokia.
The Orange and T-Mobile brands will remain in operation, offering 2G and 3G mobile services.
Ernest Doku, telecoms expert at uSwitch.com, said that today is an "incredibly exciting development" for the mobile market, and praised EE's ambitious aim to reach around 70% of the UK with 4G by the end of 2013.
"If Everything Everywhere (EE) can pull it off, Britain will officially be in a new digital era," he noted.
"For the first time, people with 4G-enabled handsets will be able to realise the full potential of their phones.
"To give an idea of what this will mean, it will take around three seconds to download a four-minute song, compared to 16 seconds using 3G. Downloading a two-hour film will take 7.5 minutes compared to the current 37 minutes with 3G."
The arrival of 4G in the UK could also enable a new generation of mobile apps built around rich media and advanced technologies, as well as kick-start new web technologies, such as HTML5.
There are clear benefits of 4G in video streaming and gaming, but also IP telephony services such as Skype and FaceTime would perform better.
However, Doku noted that anyone wanting to benefit from 4G will have to invest in the latest smartphone, which "could be a cost too far at the moment for some cash-strapped consumers".
"EE is an entirely new brand and looks set to shake up the mobile market," he said. "While the cost of its 4G data plans remain to be seen, if it comes at an appealing price point it could convince many to switch."
EE has not yet indicated how much it will charge for access to 4G services, or what kind of bandwidth limits there will be imposed. Details on that are said to be 'coming soon'.
"There is no doubt this will give a much-needed boost to the industry and economy and help put the UK back at the forefront of mobile technology and innovation," he said.
"Our customers are increasingly using their smartphones and tablets to browse the web and 4G will bring ultra-fast internet speeds that will significantly improve this experience."
Not everyone is so enthused about EE's arrival. Rival operators, such as O2 and Vodafone, have criticised media regulator Ofcom's decision to allow Everything Everywhere to reuse its existing 1800Mhz spectrum to launch 4G.
They feel that it was unfair for the firm to get a significant advantage by launching the UK market for 4G around a year before other operators could join, and have threatened legal action.
Kester Mann, senior analyst operators from CCS Insight, said that despite the "uproar" from other mobile firms, today's launch of EE represents "an impressive push by Everything Everywhere to drive 4G in the UK earlier than expected".
"With live testing beginning this week and commercial deployment 'in a number of weeks', its intention to make London 'the most 4G European city' is to be applauded," she said.
EE has already confirmed that it will offer five 4G phones this year, including the Samsung Galaxy S3 and Nokia Lumia 920, but all speculation is focused on whether the rumoured 4G iPhone 5 will also hit the UK.
Mann noted that EE indicated that more 4G devices were "coming", but she feels that the firm has enough handsets already to make this a success.
It could be juggling the EE, T-Mobile and Orange brands in consumer's minds that gives the company its greatest headaches, she noted.
"The Operator has confirmed five 4G phones from Samsung, Nokia, HTC and Huawei with more devices coming," she said.
"While it's made no mention about availability of the iPhone, this better-than-expected handset availability will inevitably help Everything Everywhere achieve good first-mover advantages, drive consumer adoption of the technology and encourage migration of customers to the new brand.
"However, while the combination of both fixed and mobile networks in a single brand ('EE') indicate a greater enterprise focus from the operator, maintaining three brands will not be straightforward.
"In particular, EE needs to be careful positioning the Orange brand alongside the premium new name."