King Helseth keeps saying to come back later when talked to. I have:
Waited outside the throne room for 24 hours
Waited outside the palace for 24 hours
Waited inside the Winged Guar for 24 hours
Talked to the bartender at the Winged Guar to exhaust Karrod before the fight
Made sure (after reading other threads here) to return to the king at least 1 hour after the time of day the quest was started (about 9.30pm in-game, so waited an hour).
I've also tried waiting an hour outside the throne room, going in and checking with the King which invariably results in the 'It is not time yet...' line, going out again and repeating for a whole 24-hour period.
As far as I can tell, he's just constantly stalling for whatever reason. Karrod himself never seems to be in the throne room, which might be the cause? I don't know where to find him, or what the refid would be to move him to the throne room or place a new version of him there.

Try this:
Try this:
1. Wait in a cell which is NOT the throne room and NOT the winged guar.
2. Type these commands into the console:
3. The first command should return a "0" or a "1". The second command should return "20". If this is correct, then type these commands:
4. Now wait at least 10 seconds and type:
5. If that returns "2", then enter the throne room and talk to the King. Select topic "Fight my Champion".