I cannot delete battle reports.
select a report, click the cross next to the report - no changes
select a report, use context menu, click delete - no changes
I am back on my island and the related adventure has ended.
Exit mail, and go back in - all still present.
I had some old battle reports pre update from this adventure, and I deleted these before returning to the adventure, which was started before the update.
Its only battle reports created today that remain