Belfield and Ballifield
[NOTE: ALWAYS A BIT DISAPPOINTING, AND SOMETIMES RATHER EMBARRASSING, TO DISCOVER THAT SOMEONE ELSE HAS BEATEN YOU TO THE PUNCH. SEE http://nq.oxfordjournals.org/content/61/1/11.short?rss=1
FOR MARK ENGLISH'S 2014 ARTICLE ON BALLIFIELD AS MAISBELI. SO EVEN THOUGH I'VE HAD THIS IDENTIFICATION LURKING AS NOTES ON MY COMPUTER FOR SEVERAL YEARS, I MUST ISSUE THIS RETRACTION. PUBLISH OR PERISH HAS MORE THAN ONE MEANING, IT WOULD SEEM. OR, PERHAPS, HE WHO HESITATES IS LOST MIGHT BE A MORE APPROPRIATE ADAGE HERE. ]
In my book THE ARTHUR OF HISTORY, I identify the Mount Damen battle of Uther Pendragon with the hill fort at Almondbury overlooking Huddersfield. Geoffrey of Monmouth's Conisborough, one of Ambrosius Aurelianus's two battles in the area, was not far distant.
But what of Ambrosius's other battle - that of Maisbeli? As has often been noted, Mais- is here for a Welsh maes, 'field' or, perhaps, 'plain.' This place would seem to be in the same general region as Conisborough.
I could propose the ancient hamlet of Belfield (also found spelled Belefield), now in Great Manchester:
However, there is one other site that has a better chance of being Maisbeli - Ballifield near the Templeborough Roman fort/settlement in the neighborhood of Sheffield.
Ballifield as a place-name is believed to be of Norse origin: