Kentmere 400 @ ISO 3200
After a little experimenting, I have (in my own opinion) had reasonable success pushing Kentmere 400 to ISO 3200 in Rodinal/R09 1+25. The appended shots were made last November at 2 PM on a "cloudy bright" day - which at 55°40'N is not very bright.
Development time was 20 minutes, with very gentle agitation every 30 seconds.
Incidentally, the prints were made on 20+ years old Orwo paper (found in an attic) and then scanned on a generic home office scanner (I apologize for the dust and cat hairs on the scanner plate).
These imperfections notwithstanding, the pictures should still convey an impression of the possibilities offered by the combination K400 + Rodinal.
Best of luck!