AJG17F wrote: …But I cannot edit it so far as I can see. If I tap it nothing happens! I'm probably being thick but my wife's newer ipad can add a caption although only to some photos but not all!
Pictures that are transferred through a cable from a computer, usually by iTunes, can be shown by Photos, but they're not "owned" by Photos. So these pictures can't be edited or deleted by Photos. The idea is that they are kept on the computer and transferred to the iDevice temporarily. These pictures usually have the trashcan grayed out, and they won't do any sort of editing. Are these the pictures that you can't add captions to?
If you want to save some of these non-deletable pictures, then you can use "Share" to save them to Files. Then re-import them from Files to create fully useable versions.
Let us know if that's it…