Heh, I was working of the top of my head. The number actually is based on c. 29,000 hides in the area of Harold's muster: the "whole of central and southern England" (that's a Freeman quote, I think; being in a hurry I can't look it up just now) - East Anglia, Northamptonshire, Hampshire, Berkshire and the "home counties". The "five hide rule" allows for 5,900 thegns/fyrdmen. By the time Harold left London for the Sussex downs, this number would have increased, not decreased, because of the five days or so so that he spent in London getting his army organized after the swift return march from York. So my minor slip of memory could be actually close at 7,000.

Anyway, the difference of an extra thousand is moot. With added troops for followers, his army is potentially quite large. but I agree that getting them all there at the same time was the challenge, and we must assume from a synthesizing of the main sources, that in fact the majority of the mustered forces he had were not on hand when the battle started.

As for the march rates: these support the mounted troops position that I adhere to. There is no way that part-time soldiers could have arrived in any sort of numbers or shape after a march of c. 180 miles in five days. But a mounted force can make the c. 35 miles per day easily and keep their horses in good shape as well, which is important. There was no emergency pushing Harold to get there any faster; he was only going north to confront the invaders, not perform a rescue. Had he been doing this march with infantry, it would have taken him two to three times longer to get to Tadcaster. The fact that he still had a large core army after Stamford bridge shows that he won that battle without suffering very heavy casualties, a further indication that his army had numeric supperiority, which further indicates that he HAD a large army on hand and could not have performed a forced march to get there (that would have exhausted his troops and left a lot of them behind on the road, having fallen out).

The evidence of heriot - the death duty owed his lord upon the death of a thegn - shows that all thegns were expected to have two or even four horses; mail and weaponry are included, so that we can assume the thegns as a well-armed force. There are enough horses just allowed the thegns alone for them to mount up at least one follower. But I see no reason to assume thegns as the only horse owners in England. the relationship of thegns to geneats ("companions") is very similar to thegns to their own lords, just on a lower social level. In other words, a military obligation in repayment for lands and privileges. It would be pointless to require military service of a geneat if he couldn't get to the battlefield wherever it was.

As for Hastings field being marshy: it is evidently far wetter today than it was back then. There have been many ponds added that were not there. (Most likely, we can't know for sure, but that is evidential.) And I believe the evidence for c. 1066 makes for a drier period between "mini ice ages". but I can't recall for sure.