Is there anything special about the way MFC treats new/delete pairing
please?

IE if my code does a new somewhere I assume I **must** do the
corresponding delete as well to release the memory allocated?

Only if you look at a typical MFC wizard generated program yo see a line
like this:

 CMainFrame* pFrame = new CMainFrame;

in InitInstance but no  delete for it.

I assume that MFC knows about this and tidies up?

MFC does a lot with new and delete to allow it to do things like allocation
tracking and memory leak detection; however, it does nothing to relieve the
responsibility of deallocating (i.e., delete-ing) the memory you allocate
with new.

What you are seeing with the CMainFrame object is a C++ trick, not an MFC
trick. You will also see that the pointer to the new CMainFrame object is
stored in a member variable of the CWinApp-derived class. When the
application shutdown, cleanup code in the CWinApp class deletes this
pointer.

Dave Smith