Research: 5G on London Underground better than city
September 2, 2026



For most of the smartphone era, the London Underground remained one of Britain’s most prominent mobile not-spots, leaving passengers without continuous cellular service while metro systems in cities such as Paris, Tokyo, and Hong Kong had already introduced tunnel coverage. That era is now ending. Under a 20-year neutral-host concession awarded in June 2021, a single shared 4G and 5G network is being built beneath London and leased to every operator.

As of August 2026, over 60 per cent of the 121 below-ground stations were live and the rest of the sites are expected to be live by year-end.


To test how real that catch-up is, Ookla analysed more than 50 million background signal scans collected across Greater London between March 25th and April 30th, 2026, using a new method that identifies high-confidence below-ground measurements at massive scale.

Key Takeaways:

Coverage on the Tube is real, in use, and concentrated where Transport for London (TfL) says it should be. High-confidence below-ground scans trace the connected heart of the network, from Shepherd’s Bush to Liverpool Street and Brixton to Highgate, and align closely with the line sections TfL’s official coverage map shows as live. Passive measurements from phones in pockets, each one recording a live connection, now independently verify the rollout.
Almost one in five below-ground connections is already on 5G. Some 19.8 per cent of below-ground scans connected over 5G, against 16.5 per cent above ground citywide, because the system was built 5G-ready from day one. Every operator shows a healthy below-ground 5G share, from 12.8 per cent on Three to 26.5 per cent on O2.
Signal strength below ground is comparable to the street above. Median 4G signal strength is -96 dBm on below-ground platforms, against -98 dBm at street level citywide (readings closer to zero are stronger). A like-for-like comparison within the same small areas shows the street still wins by 2 to 3 dB, but holding within a couple of decibels of the open street inside 19th-century tunnels reflects a network built into the stations and tunnels themselves.
The signal holds to 30 metres down, and 5G is live at the deepest measured platforms. Median 4G power readings stay between -94 and -96 dBm across the first 30 metres of estimated depth, falling to -101 dBm beyond that, while the share of connections on 5G declines from 21 per cent in the shallowest band to 14 per cent in the deepest. Where 5G is present below ground it is strong, with a median 5G reading of -93 dBm, stronger than the above-ground citywide 5G median of -98 dBm.
All four UK operators are live on one shared network, and customers use it in proportion. Below-ground connections split EE 33 per cent, Three 24 per cent, Vodafone 21 per cent, and O2 20 per cent, with the remaining 2 per cent on MVNOs such as Sky and on international visitors roaming onto UK networks. No other UK mass transit deployment has matched that tenancy mix. London locked it in before the first major post-pilot expansion, with all four networks signed by July 2022 and the Emergency Services Network (ESN) providing a separately funded public service workstream.