One of the places in the UK capital where mobile connectivity is strongest is up to 30m underground, as more stations and tunnelled sections of the Tube network across London now have 4G and 5G mobile coverage as part of the ongoing development project between Transport for London (TfL) and Boldyn Networks.

TfL carries up to four million passengers a day on the London Underground network, and renewing and preparing the communications network for the future has long been regarded as essential to maintain and improve critical infrastructure. Before it carried out its first expansion work, TfL noted that legacy systems can slowly become unreliable and disrupt services, leading to delays and an overall negative impact on passenger journeys.

All of the three mobile network operators – VodafoneThree, EE and Virgin Media O2  – are taking part in the roll-out, as part of the Mayor of London’s and TfL’s stated commitment to bring mobile connectivity to the whole of London’s transport network.

The expanding coverage will host the new Emergency Services Network (ESN) which, when fully operational, is designed to give first responders immediate access to life-saving data, images and information in live situations and emergencies on the frontline.

Boldyn Networks was awarded a 20-year concession by TfL in June 2021 to deliver high-speed mobile connectivity across the entire London Underground network, creating a backbone of mobile and digital connectivity across the network to all ticket halls, platforms and tunnels on the Tube network, with total network coverage targeted for some time in 2026.

Around 400 engineers are regularly working on the project overnight, delivering the project during the limited overnight engineering hours on the Tube network. Boldyn is also committed to installing a fibre backbone across the capital to improve connectivity both above and below ground.

TfL and Boldyn are working to introduce high-speed 4G and 5G mobile coverage across the whole Tube, Docklands Light Railway (DLR), Elizabeth line network, and the Windrush line between Highbury & Islington and New Cross. Following full interoperability testing being completed across all Tube lines in 2025, design and initial testing work is now underway on the Windrush line and DLR, ahead of the tunnelled sections and stations getting coverage later in 2026.

Alongside the whole of the Elizabeth line, which was completed in December 2024, 62 out of 121 Tube stations which are located “underground” now have begun receiving mobile coverage in their ticket halls, corridors and platforms. Key stations including Euston Square, Cannon Street and Battersea Power Station have recently gone live with 4G and 5G mobile coverage, with more – including King’s Cross St Pancras, Gloucester Road, Warwick Avenue and Vauxhall – set to go live in the next few months.

TfL also revealed that work to extend coverage in the tunnels along Tube lines was continuing to “make good progress”, with the first sections of the Circle and District line between Blackfriars and Cannon Street, and between Notting Hill Gate and Bayswater, now live. TfL and Boldyn are working to introduce more sections as quickly as possible during 2026 and they expect “the vast majority” of the Northern and Metropolitan lines to have coverage in the tunnels by end of summer 2026.

Work to deliver mobile coverage across the whole Tube network will continue throughout 2026, with work focusing on sections of the Circle and District line, where a number of stations already have limited mobile coverage due to being closer to the surface, as well as along the Victoria, Jubilee, Bakerloo and Piccadilly lines. Installation work will also continue along sections outside of Central London, and where smaller tunnelled sections need to be treated individually.

Installation work is already taking place alongside the planned escalator works at Cutty Sark Docklands Light Railway station to help ensure that customers can benefit from mobile coverage at this station as quickly as possible.

Alongside installing mobile coverage across the Tube, TfL and Boldyn are also working to install small-cell mobile technology on TfL assets, such as lighting columns, to enhance mobile connectivity in high-footfall urban areas. Some of the capital’s busiest areas such as King’s Cross, Waterloo, London Bridge, Old Street, The Shard and Hyde Park Corner already have such connectivity.

Commenting on the network and the aims of the project as a whole, Isabel Coman, director of engineering and asset strategy at TfL, said: “It’s great to see further progress in our goal to introduce high-speed mobile coverage across our Tube network…We are on a clear path towards having 4G and 5G mobile coverage across the whole network by the end of 2026. Engineers are working hard overnight during the limited engineering hours to deliver this programme.”

Boldyn Networks UK & Ireland chief operating officer Nick Hudson added: “Our long-term partnership with TfL to extend reliable 4G and 5G mobile coverage across the London Underground is grounded in improving everyday journeys for millions of people. A project of this scale demands extraordinary engineering effort and close-knit collaboration with TfL, with work often carried out overnight in one of the world’s most complex transport networks.

“We’re immensely proud of what’s been achieved so far, and each section completed brings us closer to our goal of creating a more connected London for those who visit the city and those who call it home.”