The GPC speaks for a "Count of Huntington" who pays homage to Aethelswith, King of Essex during Anarchy (providing the Saxons with Knights). Per Book of the Warlord, there is no count of Huntland (Huntington), and not only that, there are not even any major Warlords who have their Caput Major in Huntland. The closest that I can find to a named "traditional authority figure" is Sir Cadellin, Sheriff of Huntland and tenant of Huntsman Castle. My understanding is that the Sheriff wouldn't normally have Knights of his own (I believe he would depend on the King's Knights if he ever had to force the issue with another Warlord?). There is no King during Anarchy though, so I'm trying to figure out if it would be better to say that Sir Cadellin just sort of "takes over" and becomes the defacto leader in Huntland, or if it would be better to have a different warlord entirely fill this role in the GPC plot. If he's an honorable sheriff I would imagine he'd just hold the castle for the next King. If he's power hungry, he might take advantage of the power void and start gobbling up what he can.

Other candidates might be Quintus, Bishop of Londinium, Lord of Grantabridge Castle (and probably not someone that would die at St Albans) or Dywel, Abbot of Eel Island who builds Eel's Island Castle during Anarchy. Quintus is interesting because he has two Castles and the Diocese of Thamesmouth, Hartland, and Berroc. He's probably the wealthiest of the Warlords with holdings in this region and may be the closest thing the commoners might have to a protector during this time period. Also, with Londinium having all the pressure from the Saxons during Anarchy, I could see it being easier for him to just turn over his Knights to Essex rather than having to pay tribute.

Whoever it is, needs to be powerful enough to provide a "contingent of Knights", so I'd assume we'd be looking at at least a couple of eschilles, so at least 200-300 libra (similar power to Baron Thornbush) to make this a meaningful event.

This is one of those things that crop up due to GPC preceding Greg's idea of going from geographically concentrated fiefs to the Norman/Angevin England's scattered fiefs (courtesy of William the Conqueror, who had first-hand experience on how troublesome a vassal with a secure powerbase, say, the Duke of Normandy, could be versus his king).

In Anarchy, however, all rules are tossed out. It makes perfect sense for those counties to coalesce around a local strongman for protection, rather than look for their distant, likely dead, liege lord half a Logres away.

Personally, I'd let Sheriff Cadellin survive the Feast and become the protector of Huntland. Just replace all 'Count of Huntingdon' references with 'Sheriff of Huntland'. This also allows you to kill 'Count of Huntingdon' off in the 501 invasion, which might be a bit more difficult if he is a bishop in Londinium.

That's exactly what I did in my current campaign: I allowed a few sheriffs and royal officers to survive the Feast.

Because of their focus on a specific area, they make great foes in the Anarchy.
It's their duty to protect their castle/county, and they secure it by force of arms.

Yep. Cadellin has the extra excuse that you can very easily have him holed up in his castle during the Battle of St. Albans: he never makes it to the Battle and hence misses the Feast, too. Same excuse as with Duke Corneus of Lindsey. They are both in the invasion path of the Saxons.

As for Count of Hertford, he is missing too (a quick search on the Barons in BotW), so you could do the same thing with the Sheriff there, or mix things up a bit and have a castellan or something take over when the Sheriff dies with Uther. The other option would be the Abbot-bishop of St. Albans, especially if you make him more of a belligerent clergyman, who would be leading his own armies during Anarchy.