It is an indirect, wholly-owned subsidiary of CK Hutchison Holdings, a limited liability Cayman Islands company registered and listed in Hong Kong.

[12] In July 2014, Three introduced the 3 inTouch app,[13] allowing customers to place calls through a Wi-Fi connection.

[14] On 24 March 2015, Three's parent company Hutchison Whampoa announced it intended to acquire the UK operations of rival mobile network O2 for £10.25 billion, subject to regulatory approval.

Fraudsters were understood to have used authorised login information to order upgraded phones, including iPhone and Samsung handsets, to be sent to customers before intercepting them.

[20][21] On 10 March 2022 Three announced it was ending its sponsorship deal with Chelsea immediately, and asked the club to remove the company's logo from its kits.

In 2010, this 2G fallback coverage began to be removed, meaning older phones that support only 2G lost access to the Three network.

[30] Three began a limited rollout of 4G LTE services in December 2013 in London, Birmingham, Manchester and Reading,[31] expanding to over a further 450 locations by the end of 2014.

[36] The network provides LTE and DC-HSDPA service as a standard feature to all its subscribers using "Ultrafast" to describe both technologies, making it (at the time) the cheapest price for 4G and the only unlimited 4G in the UK.

Furthermore, it involved the creation of a dark fibre network to connect 20 new data centres, alongside deploying carrier aggregation across 2,500 sites, improving performance on 4G.

Until 2009, Three subscribers in the UK, Ireland, Austria, Italy, Denmark, Sweden, Hong Kong and Australia could use their service on Three networks around the world for no extra charge with "3 Like Home".

[42] The service was relaunched on 30 August 2013 as "Feel At Home" for UK customers visiting Australia, Austria, Denmark, Hong Kong, Ireland, Italy and Sweden, where calls, texts and data could be consumed without roaming charges; meaning they cost the same as for communication within the UK.

Additional countries were subsequently added to "Feel At Home" including Finland, France, Indonesia, Israel, Macau, New Zealand, Norway, Spain, Sri Lanka, Switzerland and the United States.

Despite promising to keep EU roaming free of charge, Three UK changed its terms and conditions in September 2021.

However, the plan was quickly blocked by the European Commission as it was expected to drive up prices and reduce competition.

[57] The deal would give Vodafone Group a 51% stake in the new business, with CK Hutchison owning the remaining 49%.

raised concerns that the merger risked lowering the quality of service and increasing prices due to reduced competition.

[59] In December 2024, the CMA approved the merger of Three UK and Vodafone, subject to conditions aimed at protecting consumers.

[60] In August 2017, Three launched a no frills SIM-only brand called SMARTY to compete against O2's giffgaff[62] and Vodafone's VOXI.