Thanks, Pat. I wanted one table to have the field plus the contents of that field.
I was doing it with an append query, but - not thinking clearly - I was trying to do it to a table that had an autonumber.
(Then realising the problem, I deleted the autonumber. To my shame, I deleted it from the wrong table. The append query mystified me by still refusing to work. After corresponding with the lovely (lovely new avatar, anyway) MoP, I discovered the mistake.)
Thanks for your advice, which I am copying and putting into my Good Advice notes, gratefully. Cheers