To select all the objects on a layer on the current spread, Option/Alt-click the name of the layer.
Then there is a colored square on the right side of that layer that indicates all the selected object. Drag that square to the layer to want to move the objects to (see illustration below), and the objects are switched to that layer.
For your prompt reply. I'll give it a try. All my books on AID only ever mention transferring one object at a time from one layer to another.
The solution you have offered works in that it makes an exact copy of the objects from the original layer within the new chosen layer, rather than just trnsferring objects to the new chosen layer. The original layer still has all the original objects.
Obviously the logical solution is then to remove the original objects from the original layer. Are there any pitfalls that I should be aware of before I start eliminating these original objects?
You didn't let go of the Option/Alt key after the first step.
(1) You use Option-Alt when you click on the original layer to select everything on the layer.
(2) Then release Option-Alt. Then drag the square to the new layer.
Holding Option-Alt in the 2nd step makes copies of the objects to the new layer. Without holding down Option-Alt, the objects are MOVED, not copied.
You were right and it works perfectly.