Dave may have been very lucky the Utilman trick worked.
Just recently tried that trick on a Windows 7 PC and it appeared that none of the tricks like renaming Utilman or Sethc worked anymore, and people were saying that there was an update about September last year that blocked all the easy tricks. On boot, the files are all restored to the original files. I assumed they would also do the same updates to Windows 8.1 and 10.
I wouldn't recommend renaming cmd.exe - copy it instead. You might lose your cmd.exe file when Windows boots and resets Ultiman to the original file.
Another way in was to get into safe mode and select the console safe mode, but Microsoft now requires an administrator login first.
This method was always a big flaw in Windows security that I think was left there because the Microsoft Tech's loved it, but I think some viruses started using the flaw.