The downloaded ISO was fine, it was the instillation media that was corrupted.
Checking the install media before installing (option in GRUB) confirmed that the original attempt had 17 files at fault. Fixed by sending /dev/zero via dd to the USB memory stick for a few seconds to kill the partition table, I was then able to use the Startup Disk Creator. ** Changed in: grub-installer (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1271934 Title: 14.04 failed to complete install with the error "The 'grub-efi- amd64-signed' package failed to install into /target/." To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/grub-installer/+bug/1271934/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs