How do I delete a batch of old mail in iOS?

I am seeking help in deleting old mail from my iPad mini running IOS8.1.3.

There are messages back to 2013 (I bought the iPad in December 2012). There doesn't seem to be any way to delete all mail from before a given date, except one by one.

Mail is set up to use POP on that account (my ISP doesn't support IMAP) and set to never delete from server (so they are still there when I get a chance to use the Mac).

PS: It may not matter but on the Mac I use Thunderbird set up to leave mail on the server for 7 days