O2 joins Cellnex to boost Brighton Main Line coverage

SOFIAH NICHOLE SALIVIO

News Editor

O2 has signed an agreement with Cellnex to join the Brighton Main Line connectivity project. The route serves more than 300,000 passengers on weekdays.

The deal gives O2 access to Cellnex infrastructure along the rail corridor between London, Gatwick Airport and the South Coast. It will support a phased rollout of mobile coverage, including 5G, across the full route in the coming months.

The Brighton Main Line is one of the UK’s busiest commuter railways, serving London Victoria, London Bridge and Clapham Junction. It carries 1,700 train movements a day and links services operated by Thameslink, Southern, Gatwick Express, Great Western Railway and London Overground.

Cellnex has been building the network under a 25-year contract awarded by Network Rail in 2021. The project uses a neutral host model, allowing mobile operators to use shared infrastructure rather than build separate systems along the line.

The shared network is intended to address long-standing gaps in mobile coverage on a route shaped by tunnels, deep cuttings and older station infrastructure. Once fully activated, the system is expected to provide high-speed connectivity across 99% of the 108km corridor.

O2 is the latest operator to join the programme after Three UK signed up in 2023. The addition of a second operator suggests Cellnex is gaining support for its model as rail passengers and regulators place greater scrutiny on mobile coverage and network resilience.

Station upgrades

Part of the work has focused on the main London stations served by the route. Indoor mobile systems are being installed at London Victoria, London Bridge and Clapham Junction, which together account for about 19% of rail passenger traffic to and from the capital from outside London.

The build includes 130km of fibre, four base station hotels to house operator equipment, 39 distributed antenna systems in tunnels and trackside areas, a dedicated station distributed antenna system at the three main stations, and 16 macro sites along the route. The three-year programme has so far required more than 129,000 working hours and more than 11,000 worker entries on the lineside and at stations.

For O2 passengers, the agreement means coverage improvements will be introduced in stages as parts of the system go live. The aim is to improve reliability for customers travelling between the coast and the capital.

Steve Cray outlined the case for the project.

Steve Cray, Managing Director, Cellnex UK, said: “Regular railway passengers will understand the frustration of losing signal mid-conversation or spending whole journeys with buffering videos. With O2 now on board, many more passengers are going to notice the difference on one of the UK’s most important commuter routes. This collaboration stands as one of the most significant end-to-end telecommunications infrastructure deployments on the British railway so far, and we are proud to be setting a new standard for the UK’s entire rail network.”

Operator demand

As a neutral host provider, Cellnex designs, plans and builds infrastructure that multiple mobile network operators can connect to. The approach can cut duplicate investment and reduce the amount of equipment needed across the railway estate.

For O2, the Brighton Main Line forms part of a broader effort to improve coverage where people travel and work. Rail corridors remain difficult mobile environments because of moving trains, variable terrain, and the engineering limits of older tunnels and stations.

Professor Robert Joyce, Director of Mobile Access Engineering, O2, said: “Our £700m Mobile Transformation Plan is focused on delivering reliable connectivity in the moments that matter most, and railway lines are a key part of that. By working with Cellnex to improve connectivity along the Brighton Main Line, we’ll be bringing improved coverage and capacity to customers travelling from the coast to the capital over the coming months.”

Network Rail, which is partnering with Cellnex on the scheme, said the line has been one of the most technically difficult parts of the railway for mobile coverage. The infrastructure has had to be installed while the route remained operational.

Paul Richmond, Head of Business Development, Network Rail, said: “Passengers on the Brighton Main Line deserve connectivity that matches the importance of this route, and our long-term partnership with Cellnex is transforming what has historically been one of the most technically demanding corridors for mobile coverage into a showcase for modern railway connectivity. A huge amount of collaboration has gone into this project over the last few years to support the infrastructure on a railway that is constantly operational. With O2 now on board, even more passengers will soon experience the benefits of this investment every time they travel.”