These days there are many readily available consumer SED self-encrypting drives and OPAL drives which encrypt all the data written to the disk memory (for SSD's) or surface, using a key that must be configured every time the disk is powered up. By resetting the key inside the drive all data on the drive is instantly lost and cannot be recovered. (This is nothing like the old BIOS password protection).
So you could put the key on a small usb storage device, and the computer will only boot successfully if you have this device plugged in at the time. You can therefore move the problem into one of destroying this usb key, and powering off or resetting the computer, or just of having enough time to send a command to the disk asking it to destroy the internal key (which is practically instantaneous).
You might further encrypt the key with another key on another usb storage device, and so need 2 keys to boot...
It is important that no one usually types in the key, for example, or they can be coerced into giving up that information.
There's an archlinux page on using OPAL disks in Linux. They were initially only supported by Windows. Note there are security implications in just hibernating or putting the computer to sleep.