Hello, little one! So a tsunami is a very big wave in the ocean that can come when there's a big earthquake underwater. Sometimes tsunamis can travel far away from where the earthquake happened and affect other places.
Now, the British Isles are a group of islands in Europe. They are not near any big fault lines or underwater earthquake areas, so it's very unlikely that a tsunami could happen there. However, it's important to always be prepared for emergencies and to have plans in case something unexpected does happen. So even though tsunamis are not likely to affect the British Isles, it's still important for everyone to be ready just in case.