London’s Underground is eliminating one of the UK capital’s most persistent mobile connectivity gaps, with more than 60 percent of the 121 below-ground Tube stations now live with 4G and 5G network coverage as of August 2026. Transport for London (TfL) and infrastructure partner Boldyn Networks are targeting coverage across the remaining stations and tunnels by the end of 2026.
The transformation represents an important test of the neutral-host network model, allowing EE, Three, Vodafone and Virgin Media O2 to deliver mobile services over shared underground infrastructure rather than constructing four separate networks.
The scale of the project is substantial. Boldyn Networks is operating under a 20-year concession awarded by TfL in June 2021, while total investment in the Underground connectivity infrastructure is expected to exceed £1 billion.
The project combines hundreds of kilometres of fibre, thousands of antennas and nine base-station hotels connecting mobile operator equipment to the shared Underground network.
Ookla Finds 5G Accounts for 19.8% of Underground Connections
Ookla analysis of 5G connectivity on the London Underground provides evidence that passengers are already making substantial use of the upgraded network.
Ookla’s Luke Kehoe analysed more than 50 million background mobile signal scans collected across Greater London between March 25 and April 30, 2026. Its research found that 19.8 percent of below-ground connections were using 5G, compared with 16.5 percent across London above ground.
The findings are significant because much of the Underground infrastructure was designed to be 5G-ready from the beginning rather than being upgraded after deployment.
Signal-strength measurements were also encouraging. Median 4G signal strength underground was -96 dBm, compared with -98 dBm above ground across London. Where 5G was available underground, median signal strength was approximately -93 dBm, versus a citywide above-ground median of -98 dBm.
However, the comparison requires caution. When Ookla compared smaller areas directly above Tube locations, street-level 4G remained around 2-3 dB stronger, while 5G availability was also a few percentage points higher above ground.
Ookla measured mobile coverage and signal strength rather than download speeds, upload speeds, latency, call reliability or network congestion. The results therefore do not demonstrate that Underground 5G is universally faster than London’s outdoor 5G network.
Network depth also affects 5G availability. The research showed that 5G represented around 21 percent of connections in the shallowest measured Underground areas, declining to approximately 14 percent in the deepest locations.
EE, Three, Vodafone and O2 Drive Underground Traffic
The operator connection mix demonstrates the importance of the shared network to the UK’s major mobile providers.
EE accounted for 33 percent of Underground connections, Three represented 24 percent, Vodafone 21 percent and O2 20 percent, while MVNO and international roaming connections represented the remaining 2 percent.
The figures underline the commercial logic behind London’s neutral-host approach. Instead of four operators individually installing extensive fibre, antennas and supporting infrastructure through difficult Victorian-era stations and tunnels, operators can connect their networks to a common physical infrastructure.
All four operators are participating in the rollout, according to TfL.
The Underground investment is also taking place as Britain’s operators spend billions of pounds modernising their wider mobile networks.
EE Targets 99% UK 5G+ Population Coverage by 2030
EE’s participation in the Underground project sits alongside BT Group’s wider £40 billion investment in UK network infrastructure during this decade.
EE is expanding its 5G+ network while increasing capacity across its mobile footprint. The strategy is designed to support rapidly increasing smartphone data consumption and emerging applications requiring greater network capacity and reliability.
One of the latest developments is EE’s 2026 5G+ network investment and technology programme, which forms part of the operator’s effort to strengthen 5G performance.
EE is targeting 99 percent UK population coverage with 5G+ by March 2030.
The operator also introduced EE Fast Lane on 5G+ in August 2026. Fast Lane is designed to give eligible customers priority connectivity during periods of heavy network congestion.
The combination of nationwide 5G+ investment and Underground connectivity demonstrates how mobile operators increasingly need to address both geographic coverage and high-density locations where large numbers of customers compete for capacity.
VodafoneThree Invests £11 Billion in UK Network
VodafoneThree is pursuing an even larger mobile network transformation following the combination of Vodafone UK and Three UK.
The company has committed to an £11 billion UK network investment programme, targeting 99 percent 5G Standalone population coverage by 2030.
Its longer-term ambition is to reach 99.96 percent population coverage by 2034, making 5G SA the foundation of its future mobile infrastructure.
The operator’s VodafoneThree network upgrade programme provides additional context for its participation in London’s Underground connectivity project.
The investment illustrates the two dimensions of VodafoneThree’s network strategy: expanding nationwide 5G Standalone coverage while simultaneously addressing difficult indoor and underground environments.
Virgin Media O2 Commits £700 Million to Mobile Network in 2026
Virgin Media O2 is also increasing investment as UK mobile traffic continues to expand.
The company announced £700 million of mobile network investment for 2026, covering new mobile masts, small cells, additional spectrum deployment and 4G and 5G network upgrades.
The programme includes the deployment of more than 1,000 GigaSites, designed to increase mobile capacity in locations experiencing particularly strong traffic demand.
The investment comes after mobile traffic on O2’s network more than doubled over five years.
More details are available through the company’s O2 £700 million 2026 mobile network investment programme.
Virgin Media O2 is simultaneously modernising its radio access network through agreements with Ericsson and Nokia. Its Virgin Media O2 RAN modernisation programme targets more than twice the 1 Tbps of additional network capacity delivered in the previous year.
£1 Billion Neutral-Host Network Changes Underground Economics
The technology behind the London Underground project is important because building traditional mobile networks below ground is substantially more difficult than installing conventional outdoor sites.
Boldyn Networks’ architecture uses nine base-station hotels, fibre infrastructure and distributed antenna systems to connect mobile operators with passengers travelling through stations and tunnels.
The neutral-host approach changes the economics because EE, Three, Vodafone and O2 do not need four completely independent sets of physical infrastructure.
Instead, operators can place equipment at central locations and connect through Boldyn’s common infrastructure.
Boldyn aims to recover its investment through operator access charges and other infrastructure revenues rather than requiring each operator to fund a complete Underground deployment independently.
The network also supports the UK’s Emergency Services Network, providing infrastructure for critical communications used by police, fire and ambulance services.
For passengers, the benefits extend beyond conventional phone calls. Continuous connectivity can support messaging, digital payments, travel information, streaming, business applications and cloud services during Underground journeys.
London Targets Complete Underground 4G and 5G Coverage by End-2026
London’s Underground network has moved rapidly from one of the capital’s most prominent mobile not-spots toward becoming a major shared digital infrastructure platform.
The headline numbers demonstrate the scale of the transformation: more than 60 percent of 121 below-ground stations connected, more than £1 billion of investment, a 20-year infrastructure concession, nine base-station hotels and more than 50 million mobile measurements analysed by Ookla.
Most importantly, 19.8 percent of below-ground connections already use 5G, exceeding the 16.5 percent citywide above-ground figure in Ookla’s broad comparison. Median Underground 4G signal strength reached -96 dBm, while available 5G averaged approximately -93 dBm.
The investment is being reinforced by operators’ wider network programmes: BT’s £40 billion infrastructure investment this decade, VodafoneThree’s £11 billion network programme and Virgin Media O2’s £700 million mobile investment in 2026.
With EE targeting 99 percent 5G+ population coverage by March 2030, VodafoneThree targeting 99 percent 5G Standalone coverage by 2030 and 99.96 percent by 2034, and O2 deploying more than 1,000 GigaSites, Underground connectivity is becoming part of a much broader UK mobile network modernisation cycle.
TfL says the entire Tube network remains on track for mobile connectivity by the end of 2026.
For mobile operators, London’s Tube demonstrates how neutral-host 4G and 5G infrastructure can extend coverage into complex, high-density environments while reducing duplicated infrastructure investment. For passengers, the result is simpler: one of London’s biggest mobile connectivity gaps is finally disappearing.
FASNA SHABEER
