Is there a way to select and delete more than one member simultaneously?

I would like to remove old/dormant forum members, I can find them using advanced search. The only way to delete that I can see is using the drop down menu that appears at the right of the searched list. Using this method takes me back to the member list each time so I have to either record a list of members to remove or search again.

Solved this one myself. I found a 'prune' option in the information at the top of the list.

I spoke too soon, I found the feature but it doesn't work. Is there a limit to the number of members that can be deleted in one go? I get the following error message:-

A configuration or server error has occurred

EX0 Something went wrong. Please try again.