The chief reasons for suggesting Wormelow Tump as the site are circumstantial. While name of the River Gamber and the location of Gamber Head are indicative (see Note), it is chiefly the place of Wormelow Tump at the centre of the communities in this area that marks it out as a potential location.
Firstly, it should be noted that the current residents of the village believe it to be the location of the tomb - there is a small display in the "Wormelow Tump Inn". This is not to be dismissed, as there has been broad community continuity in this area, albeit under different management, since recorded history began in the region. While, it seems very likely this reflects recent Arthurian worker's opinions rather than a native tradition, its hard to be definite.
The chief reason Wormelow Tump is historically recorded at all is its place as the long-term centre of the social structure in this area. Wormelow (Urmelauia) is recorded in the Domesday Book as being the meeting place of the Hundred (or possibly Shire) Court, to which any (free man?) with a horse in Hereford had to go three times a year*. The court system certainly appears inherited from the period of Saxon rule and the name "Wormelow" is composed of Old English/Anglo-Saxon terms, backing up its importance to the Saxons. The Old English term Hla(e)w, which has now corrupted in placenames to the "Low" component*, indicates a mound - so it is likely the tump was there during Saxon times at least (see Note on name).
However, this is not to say it was any older - the picture is confused by the fact that the Anglo-Saxons were known to build their own mounds to meet at, but also to reuse old burial mounds for the purpose (in addition, they were also known to reuse older mounds to bury their dead)*. It should be noted that there has been at least one suggestion that Hlaw referred specifically to either mounds reused for burial or new Anglo-Saxon burial mounds, while beorȝ ["bergh"] (related to hearg*?) referred to older untouched burial mounds*. This may point to Anglo-Saxon remains/contamination at least at Wormelow (thought the name split may have a north-south divide as well*). While there doesn't appear to have been an archeological investigation prior to the mound's destruction, Andere* notes that
An elderly gentleman who had heard I was interested in trying to trace whether the Tump had ever been excavated, kindly phoned and informed me that when, in 1885, as a trial test before attempting excavation (an attempt subsequently not made), a two-pole section was taken through the mound at mid-height, nothing was found. Finally a vertical was attempted, but nothing was discovered, apart from a few bones and some ashes. I asked if the ashes were in an urn or any other sort of vessel, but he could not sat, nor what had happened to them after that.
As it is not clear whether the Saxons used their own meeting places as burial mounds this doesn't give us much to go on either way, other than to confirm that the mound was one of the relatively rare (1 in 12*) Anglo-Saxon meeting mounds that were also burial mounds. If it did turn out the tump at Wormelow was Anglo-Saxon, it is of interest that the meeting-function isn't noted (unless the measurement reference is meant humorously!) and the fact that it is in Anglo-Saxon territory isn't mentioned - which it is for other wonders in the list. The general fact that the Saxons aren't mentioned suggests the list dates from prior to the Saxon incursion into this area, though there was a good deal of fluctuation in control of this region.
It is likely that Anglo-Saxon meetings in general in Britain go back at least to the early 9th C.*, but, of course, it is possible the meetings at Wormelow also extended further back (the name and location may suggest at least a pre-10th C. Saxon use*). The fact that the location was positioned at the rural junction of five roads (plus two minor tracks), and not in the major town of the area, says something about the power structures in place when it was set up - while these certainly appear to be the Hundred system of the Saxons, it is not clear what prior system was in place. The Domesday book makes it quite apparent that this was a rare legal location, in which Saxon law continued in the presence of Norman/French rule but with particular rules for the Welsh in the area*. More work would be needed on the layout of the road system in the area and its interrelation with the mound and surrounding villages of various ages before anything definitive could be said. However, one thing is clear - the tremendous continuity of form in this area. Not only is Wormelow still a major junction in the local road network, but it still represents the junction between a number of administrative units (three census wards and three parishes), just as the meeting place probably did for the Saxons*. In addition, within Wormelow itself, the area of the meeting place may have been preserved by the village form (see Note on tump location).
Thin reasoning though the importance of Wormelow Tump is, it does indicate that this, of all the possible locations within the area, has held an unusually significant importance for the local people. For that reason alone it deserves some consideration.