I was sent a file that someone else had created in Autocad. It contained the model view and a single sheet with a viewport. Inside the viewport the view was rotated with respect to the model space.

I wanted to see how this had been done and spent some time researching the topic online. To get this effect most people recommend using a Custom Coordinate System. You activate the drawing inside the viewport and then use the command like "CCS Z 60" to specify a rotation. Then use "PLANVIEW A" to display the result according to the new coordinates.

In this case there was no CCS in use, so I couldn't work out what was happening. It turns out that Autocad has additional commands to rotate the view without changing the coordinate system. These have names like "DVIEW TWIST" and "MVSETUP". These are not available in DraftSight. But the good news is that DraftSight does correcly honour the setting when it opens a file that contains this feature.

Moreover, DraftSight will display what is happening if you type the unlisted command "VIEWTWIST". This displays the rotation angle in the current viewport as a read-only value in radians. To regain control over the rotation, reset the view to WCS, then apply a rotated CCS as described above.

So well done DraftSight and problem solved.