I know very little about this machine or the company behind it. Scant info is available on the web so hopefully some mailing lists will come up trumps
Cambridge Systems Technology (a "backronym" apparently) was started by David Oliver and Graham Priestley after they (and lots of others) left Torch in Cambridge. They both knew the Sinclair QL was a good machine at heart so they used it as a basis for their first range of machines.
The single 720k floppy drive Thor 1F
The dual 720k floppy drive Thor 2F
The 20mb SCSI HD Thor 2WF
All these machines were designed round the QL motherboard, so unnecessary items like the keyboard and microdrives were discarded and a new board designed that connected to the QL's expansion port. This new board contained extra memory to take the base up to 640K, a ROM extender board and a WD disk controller to give the machine floppy and hard drive capability.
Also on the new board were an RS232 port, an AT-style (but not compatible) keyboard port, centronics port and the QL expansion port replicated out the back of the machine. Access to all the other QL ports was provided too with holes on the back of the smart and rather heavy new metal case everything lived in.
The system ran a modified QL operating system and included the TSL task sequencing language similar to the ICL OPD/Merlin Tonto so you could run up to 6 instances of the bundled Psion Xchange application suite (again as on the OPD/Merlin) and share data between them. Pretty good for its day! Pity my machine doesn't have its HDD any more so I might not get a chance to find out what the new front-end looked like :-/ I've found public domain versions of Xchange on the web however, so at least I can get that running once I get a hard drive.
Based on the info found at the same Xchange site the production of Thors stopped in 1989 because of cashflow problems.