Some caveats for the above.
The tool did not go straight in, it wandered a bit. I found that moving the carriage back and forth a teensie amount kept it cutting reasonably on track.
The second chunk (rhs in photo) I experimented with that dangerous method of using the hacksaw in the lathe whilst it was turning. It worked very well and by angling the blade first to one side then the other whilst sawing kept it moving easily. Imaging sawing an "X" in the metal, thats why you can see all the saw marks on the face of the second cut.
I was getting ready for it to grab but it didnt.