Uswitch warns of mobile signal disruption at London Marathon

Uswitch has warned London Marathon runners and spectators to expect mobile signal disruption at key points along the route, particularly in crowded areas such as Tower Bridge, Canary Wharf and The Mall.

When large numbers of people try to get online at once, pressure on local mobile infrastructure can lead to delayed live-tracking updates, patchy calls and slow data speeds. The issue is more likely to be network capacity than a lack of coverage.

More than 59,000 runners are expected at the start line, with large spectator crowds gathering across central and east London. Areas expected to be especially busy include Tower Bridge, Canary Wharf, Embankment, Westminster and the finish area on The Mall.

Archie Burkinshaw, Mobiles Expert at Uswitch, said the problem often arises even when phones appear to have a strong connection. "On marathon day, some of London's busiest spots can put mobile networks under pressure as thousands of runners and spectators try to get online at once."

"It's often not a coverage problem but a capacity issue, as local masts can become overloaded by the number of devices trying to connect at the same time. This can create digital gridlock, leading to slower data, delayed live-tracking updates, patchy calls, and difficulty uploading photos or messages."

"In some cases, people may still see full signal bars, but performance can lag because the network is congested.

"If you're worried about losing connection, one option is to have a backup eSIM ready on another network. Most newer phones let you keep your usual number active while using the second network for data, although busy areas can affect multiple networks.

"A few quick checks before you leave can make all the difference: download maps, save tickets or travel information, agree on a meeting point, and pack a portable charger."

Practical steps

Suggested measures include downloading offline maps and transport information before travelling, taking screenshots of QR codes and tracking links, and agreeing meeting points away from the finish line. The advice also includes carrying a portable charger and using low-power settings to reduce battery drain.

In especially crowded areas, switching from 5G to 4G may help, as 4G can sometimes provide a more stable connection when networks are under strain. Users are also advised to send SMS or other low-data messages rather than trying to upload video from the busiest sections of the course.

Another option is to install a secondary eSIM on a different network before race day. Some one-month eSIM plans are available from £2.50 for 100GB, according to the guidance, although service problems can still affect more than one operator in the same location.

Route pressure

The warning reflects the dense spectator crowds that build at marathon viewing hotspots, where sudden demand can put nearby mobile masts under strain. Moving 100 to 200 metres away from the busiest part of a crowd may improve service.

Runners are advised to prepare for periods of limited connectivity by downloading playlists and maps in advance and avoiding live uploads during the race. Participants using GPS sports watches may also want to put their phones into aeroplane mode to preserve battery life until the finish.

Guest Wi-Fi in pubs, cafés and restaurants along the route may provide an alternative if mobile data becomes unreliable. Users can also try manually selecting a network before returning to automatic settings if their phones remain attached to a weak connection.

The London Marathon is one of the UK's largest mass-participation sporting events and draws substantial crowds across multiple boroughs, making it a recurring test for mobile networks in the capital. With tens of thousands of runners and spectators relying on live updates, messages and navigation throughout the day, the key advice is to prepare for congestion before leaving home.