These 2 systems have co-existed since late 2014 (Windows was 8 back then, ubuntu can't remember 14?)
Unfortunately, the latest window update appears to have trashed the boot loader - the computer boots straight into Windows, when I "advanced restart" and go into the BIOS the ubuntu partitions can no longer be seen.
I can see them if i use bcdedit in windows, and a Ubuntu install usb also finds them.
How can I restore the boot loader to its former glory? I think it was grub2 - it's whatever the default was back in 2014