Llacheu's grave in Crickheath?
(Source: Arthur in Early Welsh Poetry, by Nerys Ann Jones)
(Source: Arthur in the Celtic Languages, by Cerridwen Lloyd-Morgan and Erich Poppe)
Llacheu, a famed son of King Arthur (and presumably Queen Guinevere), was traditionally believed to have died in battle and was buried in an area called Llech Ysgar.
It is believed that this 'Llech Ysgar' is to be identified with Crickheath Hill, near Llanymynech on the border of Shropshire and Wales. This is a very curious location to me as this is located just to the south of Oswestry, Shropshire:
In the northern part of Oswestry, there is an Iron Age Hillfort site known as Old Oswestry, which local folklore refers as "Hen Dinas" ("the old city") or, more relevant to Arthurian Legend, "Caer Ogfran/Ogyrfan" - "Ogfran" being the name of Guinevere's father in the Welsh tradition with Old Oswestry thought of as her birthplace.
If so, then the placement of Llacheu's grave in Crickheath becomes very interesting, for if he really was Guinevere's son, then he could've fought and died, possibly in defense of, his mother's home province.