For some reason three of our four logical drives have become uninitialised overnight.
C: and D: are on the same RAID array but separate logical volumes/disks in Disk Management
E: and F: are on their own RAID arrays of 33TB and 24TB respectively.
C: is working (thankfully!) so I can browse and deal with TestDisk. (I've used it numerous times at home for laptop hard drives etc so i'm comfortable using it)
Testdisk sees all four Disks and can List the data on them all so the RAID arrays and disks are not an issue.

D: should be 3.5TB occupying the full disk, but when running a standard Analyse/Write it found and wrote the MBR with a 2TB partition in the middle of the disk as you can see.
I haven't tried writing E or F yet until I can get D working. (E and F are our business backups so I don't want to mess them up!)
I've seen a few suggestions to go Advanced > Boot > List > Write, which I have also done (TestDisk can list files/folders all day long so the data is definitely still safe, it's just getting the partition record right that i'm stuck with), to no avail.
How do I get TD to write a 3.5tb partition that occupies the whole disk, per the original partition?

Doing a Quick Search starts at 0% then jumps to 58% once it's quickly found the first bit, but I don't understand why it's finding a 2tb long partition at all.
Peter