Actually, I'm sure Mr Zephaniah has been a guest on QT in the past. As has Billy Bragg.
To explain, the panel normally consists of representatives of the 3 major UK parties, Lab,Tory,Lib-Dem. and appearances by one from the smaller parties, plus someone from Left field, who has maybe an interesting slant on life. It generally works IMHO.
But this thread is more lighthearted...My 4 panellists? mmmm.
Well the whole of human history is a bit big, so I'll stick with the 20th century.

1. Hitler (justifying the Holocaust)
2. Churchill (justifying the bombing of Dresden)
3. Stalin (justifing the Gulags)
4. Pol Pot (justifying the Killing Fields)

The audience to be made up of the souls of the victims.

Just my two pennorth, but I've obviously never met any of these characters, and it would be interesting to hear thir views.