(Answering my own question)
The disc can be read using a Linux distribution. The disc uses a RAID filesystem which also cannot be read immediately. However, using mdadm it can.
I located the correct partition (sdb6) of the disk using GParted (fdisk should also work). I guessed it was this partition because it was by far the largest on the disc.
Then I assembled the RAID device (to md1) using mdadm:
mdadm -A -R /dev/md1 /dev/sdb6
I could then mount it normally using
mount /dev/md1 /media/backup
