have updated my keywords by exporting, editing them in Notepad to use hierarchy as I should have done. Originally, just put all towns into "Places". In the end I didn't know where a particular place was. So now there are Places/Country/Town/Suburb and so on. Imported them back into Bridge by Clear and Import". This appeared to work correctly, with the town of Edinburgh showing under Scotland and so on.
However, it wasn't until I searched Bridge for a particular town, the problem started. All pictures showed correctly, with the keyword in the correct location. On clicking on one of the pictures, an additional keyword appeared on top of the list in Italic letters. If I deselected that one, both of them disappeared. How can I fix that without creating 100,000 new ones?