I misread the one word in Alford’s text which I queried: when magnified, I see it is not nimiùm but nimirùm.
Nimirum would commonly imply certainty not doubt, although in some contexts it is seemingly (see Sir W. Smith’s Dictionary) used ironically; and Jean Baptiste Gardin Dumesnil (Synonymes latins et leurs différentes significations avec des exemples tirés des meilleurs auteurs, 1777) states that it is also used for scilicet. But in any case it is clear what it’s referring to in the sentence ‘ibi … ubi …… ‘. The battle was fought in Devonshire, Camden conjectures, there (namely) where the river Taw, wider than (or ‘widened by’) the waters of the river Torridge, makes for the Severn sea.
So Alford may not have been expressing scepticism regarding Camden’s suggestion, though neither is he affirming its truth. On the other hand, writing some thirty-odd years earlier, the Devon-born topographer Thomas Westcote, gent (bp. 1567-1637?), in A View of Devonshire in MDCXXX was less non-committal. He refers to the stories surrounding ‘Castle Hennaborough’, ‘Kenith-Castle’, Hubba the Dane and Whibbestow-Hubbastow and remarks:
“But to tell you truly, I find as many places in this county claim the honour of this victory, as cities in Greece for the birth of Homer.”
Interesting to note that he calls the ancient remains ‘Castle Hennaborough’ – almost 200 years before Vidal’s locals informed him that his ‘Kenwith or Kenwic Castle’ had only been been known locally as Henni Castle or Henniborough. In 1630 Westcote knew both names, though whereas remains of Castle Hennaborough may be seen, a certain mythical existence attaches to Kenith-Castle, which is also ‘hereby’. Westcote does not appear to equate the two.
Of these two names, Henniborough and Kenwith, the first presumably goes back to Saxon times, hēan+ēg+burh (as in Great Henny, Essex, Domesday 1086 Heni). Even now standing in the potential flood area of Kenwith Stream, Henniborough would then have been the ‘fortification in a high place (partly) surrounded by water’. When Benjamin Donne marked ‘Henny Castle Olim Kenwith’ on his 1765 map of Devon, it might more correctly have been ‘Kenwith Castle Olim Henny’.