How do I 'refresh' the cover?

I opened an epub with the editor and 'trimmed' the cover to neaten it up.

Saved the epub, but the new cover did not show in the book area.

I remembered that the cover image is stored in the databasee, so using the main metadata display I removed that cover and got the generic image.

Opened the epub in the editor and now the generic image is the new cover

How can I 'refresh' the metadata display and dtabase to show the new cover from inside the epub, i.e. cover.xhtml, after editing?