So I was doing a migration the other day, and due to poor planning on my part a situation has now arisen where certain subfolders (each subfolder relates to a single property) now contain over 5000 items. I need to delete all this migrated data (by filtering on the booked property field and the creation date) but I can't even SEE it thanks to SharePoint Online's immutable list view threshold (thanks again, Microsoft).
How can I delete the items that match the conditions specified now I can't even see them in the browser? I suspect possibly via CAML or somesuch but I'm unsure how to go about it and I really need a quick answer as it's part of a project that should've been finished by now, but isn't due to a) technical issues like this and b) client changing their mind every day about one thing or the other.