I have lived near Dorchester for many years. Evidence from charters (legal documents showing transfers of land or rights) indicates that King Alfred came to Dorchester and presumably he would have had some sort of base there. But where exactly was this?
Clues about Dorchester’s Saxon past are scant, and this includes any evidence that might help us establish the location of a Saxon royal residence at the time of King Alfred. My personal speculation, which I have heard others suggest as well, is that the royal site would have included the location on the northern edge of the town where the current prison buildings are sited, where we know that the Norman castle was also located. It seems to make sense that if a site was deemed defendable by the Saxons (which a royal site would need to be) then it would hold a similar appeal for the Normans. It therefore seems plausible that the Normans would have built their castle on the site of the previous Saxon fortification/royal residence. There is a very pleasant footpath that follows the River Frome and which passes below the site of the former castle. From there one can understand how elevated (and therefore defendable) the site would have been.
It has been suggested that King Alfred spent every Christmas at a royal manor at Fordington, which is now part of Dorchester but was once a separate settlement to the east. I have also read that Fordington became a royal manor after the Romans left and that the first church there had been built about 857, and that this was a royal church dedicated to St George. Although the earliest parts of the current St George’s church date to the 11th century, it is located at the site of a Roman cemetery so the location was clearly a significant one stretching back to ancient times, which makes the presence of a church being there in 857 seem more plausible.
So, we have two potential royal locations that are close to each other, one in the centre of Dorchester at the site of the former prison, and the other at Fordington. Although the evidence from charters suggests that Dorchester really was a royal location, I am not aware of any charters having been issued from Fordington. It is perhaps possible that a royal residence at Fordington would have been close enough to Dorchester to go under that name, or that the residence was at Fordington while the charters were signed at nearby Dorchester. Fordington is so close to Dorchester that I found that I could walk, at a brisk pace, from St George’s church in Fordington to the closest point of Dorchester’s former Roman walls in a matter of three minutes. It seems to me that the Roman walls (perhaps replaced or repaired in places) would have been present in Alfred’s time and would have probably continued to define and defend the town. This is supported by the fact that even today much of the line of the walls can still be followed. The exception to this is the northern section stretching between Northernhay and Salisbury Street where it is possible that there was no wall at all, with the River Frome providing defence instead. My personal opinion is that there would have been a wall here as well, which has long since been destroyed and built over. A recognition that the town was walled leads to a discussion about the location of gates through which King Alfred might have passed, including when Alfred was pursuing the Vikings from Wareham to Exeter, and perhaps passing through Dorchester, in 876.
I go into more detail on the gates and the charters in my book.