The mobile operator announced on Monday (10.06.19) their plans to launch the high speed data service to the British capital, and to bring 5G mobile and home broadband to 25 towns and cities before the end of 2019.
The Hutchison-owned firm's Chief Executive, Dave Dyson, said: "It's clear that consumers and businesses want more and more data.
We have worked hard over a long period of time to be able to offer the best end-to-end 5G experience. 5G is a game changer for Three."
Three follow in the footsteps of EE, who overtook Vodafone with the announcement of their 5G service being rolled out in six cities in the UK last month.
The mobile network - which is a division of BT - brought the first phase of their high-powered service to London, Cardiff, Edinburgh, Manchester, Birmingham and Belfast on May 30, four days ahead of their rival.
BT Consumer CEO Marc Allera commented: "5G is going to give customers in the busy areas an uplift of 150Mbps on average and often more than that. This is a premium experience.
"We are confident that some customers will break the 1Gbps milestone. When we launched 4G in 2012, we were talking bout 12-15Mbps and hat was game changing.
"But it's not about peak speeds in peak conditions - it's about reliability. Our 5G strategy is demand led and focuses on the busiest areas of busiest cities. These sites make up eight per cent of our network sites but carry 20 per cent of our data traffic. These are the areas our customers need it most."
The first phase will last until 2022, when the newest technology will be available. Whilst the third phase will launch in 2023.
Vodafone on the other hand are offering 5G in Birmingham, Bristol, Cardiff, Glasgow, Manchester, Liverpool and London on June 3rd.
And by the end of the year, they are planning to launch 5G in Birkenhead, Blackpool, Bournemouth, Guildford, Newbury, Portsmouth, Plymouth, Reading, Southampton, Stoke-on-Trent, Warrington and Wolverhampton; a total of 19 cities.