Original poster, realistically, likely most secure option to get the job done, reputable, but they are somewhat pricey
http://www.shipndestroy.com/
Had contacted them last month about destroying a few dozen 3.5 inch floppy disks over 20 years old with company data, and they responded to my initial email within a couple of hours. Included in their shipping charges with a restricted locked secure shipping container was over $40, which in my case decided not worth it, but you may decide otherwise for your needs. In my case with floppies, found destruction instructions on wiki, but likely not so easy with a hard drive.