Select all and delete in outliner search results Here's my problem...

I have many objects which I've duplicated but didn't notice myself duplicating the camera while I was in side view:



Now this is ok, because I've spotted a search box. I can find/delete...



Except deleting (while mouse is in 3D view) only deletes the one white-selected camera. The a key does toggle a form of selection, but instead of being an actual selection it's more of a doesn't do anything at all selection. The outliner is pretty unresponsive to what I would think of as typical user interaction.

How do I actually-select lots of things in the outliner?



I have just noticed that without search results I can make a doesn't-do-anything selection, right click and choose "select" to create an actual-selection. Either a all or b box select works to make a doesn't-do-anything selection. I can't however create typical shift-select between first and last so I think I need a bigger monitor to display more outliner for my box select. This right click "select" method doesn't work on doesn't-do-anything selections after filtering the outliner with the search box.
Selecting in the outliner would mark its list items as selected but does not select the objects you want to remove. To select more than one object in the outliner you can Shift-LMB each object.

Instead you could select them by name in Object Mode Menu:Select / Select pattern, Type Camera.* (this omits the default camera) and press X.