A black spot (or "not-spot") is a location with no mobile signal — or signal so weak it's unusable. Black spots are a fact of life on every UK network.
Common causes
- Geography: valleys, deep cuttings, dense forest
- Buildings: thick concrete, basements, lift shafts
- Distance: too far from the nearest tower
- Spectrum: high-band 5G doesn't penetrate walls well
Why multi-network helps
Black spots on one network are rarely black spots on all four. EE might have no signal in a rural valley, but O2 might have a tower the next hill over. A multi-network SIM like Fuse switches to whichever network has any signal where you are.
When all networks are dead
Some places (deep tube stations, certain rural valleys) have no signal at all. In those areas, Wi-Fi Calling — using a local Wi-Fi network for voice — is often the only fix.