Thanks Kirk
Your previous explanation was enough but this makes the process clearer and I've now sorted out the collection keywording.
An anomaly that this has thrown up is in the number of files found:
View/Combined images is off
A search for "" finds 335,959 images
A search for (?-i)collection ^"Race deduped files for Northants" finds 4,513 images
A search for (?-i)collection is not ^"Race deduped files for Northants" finds 331,579 images
Adding the last 2 search numbers gives 336,092 images that are either in the collection or not in the collection. I'd expect that to be the total number of images in the catalog but the first search shows that to be 335,959 images, a difference of 133 files. These 133 images seem to be both in the collection and not in the collection. I'm baffled. Do you know what's going on here?
David