A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
Solved.
A background graphic is editable in one of the slide masters.
View / Slide Master / select the first or top master in the left pane of masters
Look for the master that has the graphics and select it. Then you can maniputlate the graphic.
With several masters you need to be careful when looking for the correct one.
I must NOT have selected the correct slide master when I tried this a few days ago.
I looked at several presentations and found that the first or top slide master is usually the one with the graphics.
Regards,
Steve