1. Switch off “automount” by running mountvol.exe /N
2. Connect disk to Windows (do not mount the disk)
3. Run diskpart
   1. Enter list volume
   2. Enter select volume X
      (where X is the correct volume number from the previous command)
   3. Enter att vol set readonly
   4. Enter detail vol and ensure the read-only bit is set

Now you can mount the volume and it will be read-only.

To re-enable automatic mounting of new volumes, run mountvol.exe /E.

To remove the read-only flag, select the volume in diskpart and in step 3.3 enter att vol clear readonly.