Why is the name of the series After Cilmeri?
Because Cilmeri was the place that Llywelyn ap Gruffydd was lured into an ambush and assassinated by the English. The series are an alternate history that occurs … after!

It has been over 700 years since Llywelyn ap Gruffydd’s death on 11 December 1282.  J. Beverley Smith writes:

“Intimations of treachery, of breach of faith, are so often conveyed darkly, and no chronicle, nor any other source, provides the unequivocal testimony which might enable us to unravel the threads in the various accounts of the tragic happening in the vicinity of Builth.  It was alleged at the time, or shortly afterwards, in the most explicit statement we have, that the prince’s decision to venture into the area was influenced by one of the sons of his old adversary, Roger Mortimer.  The Hagnaby chroinicler, an important source for the events of the day on which Llywelyn died, was quite definite:  Roger Mortimer, he says, but, more correctly, his brother Edmund Mortimer, drew the prince there by beseeching him to come to the neighbourhood of Builth to take his homage and that of his men. Along with other lords he hatched a plot to corner Llywelyn and kill him”  (Llywelyn ap Gruffydd, 1998:551).

The chronicle of Hagnaby Abbey is a historical document that begins in 1173 with the foundation of the Abbey in Lincolnshire.  It is now ruined.  It was a house Premonstratensian canons, “founded in 1175-1176 as a dependency of Welbeck Abbey. It gained independence and abbey status in 1250, and was supressed in 1536.”   http://www.pastscape.org/default.aspx

http://www.bl.uk/onlinegallery/onlineex/illmanus/cottmanucoll/c/011cotvesb00011u00009v00.html

Whatever really happened, the entry from the Chronicle of the Princes (Ystrad Flleur) says it all:

And then Llywelyn ap Gruffudd left Dafydd, his brother, guarding Gwynedd; and he himself and his host went to gain possession of Powys and Buellt. And he gained possession as far as Llanganten. And thereupon he sent his men and his steward to receive the homage of the men of Brycheiniog, and the prince was left with but a few men with him. And then Edmund Mortimer and Gruffudd ap Gwenwynwyn, and with them the king’s host, came upon them without warning; and then Llywelyn and his foremost men were slain on the day of Damasus the Pope, a fortnight to the day from Christmas day; and that was a Friday.
—-Brut y Tywysogyon, Peniarth manuscript 20  (The Chronicle of the Princes)

His head was carried to King Edward I, who ordered that it be displayed on a pike, in London.  Apparently, it stayed on display for over 20 years.  The rest of his body is purportedly buried at Abbey Cwmhir, northeast of Rhayader in Powys.

Llywelyn’s brother, Dafydd, was eventually captured and hanged, drawn, and quartered, the first man of significance to experience that particular death.  His death was practice for what Edward did to William Wallace, two dozen years later.  Gwenlllian, Llywelyn’s daughter and only child, was kidnapped from Aber and sent to a convent in England, where she remained a prisoner her entire life.

Cilmeri is a small town to the west of Builth Wells. King Edward built a castle there, which is now a couple of mounds and ditches in the middle of a housing development.

Buellt Castle (Builth Wells for the English) was the seat from which the Mortimers lured Llywelyn ap Gruffydd to his death near Cilmeri on 11 December 1282.  It was a major Edwardian Castle of its time, but all of the stone work as disappeared.

“Builth is nothing more than a series of earthworks – nothing visible remains to give testimony to the structure which once stood at the site. By 1183, documents record a clash here between the Welsh and Normans, and much of what we see reflects this original motte and bailey fortification. During the next 90 years, the castle saw repeated conflict and changed hands between the Welsh and English on several occasions. By the 1240’s masonry structures were established at Builth; however, it was as the result of Edward I’s initial campaign against the Welsh in 1277 that Builth’s modest stronghold was refortified and transformed into a formidable fortress.

I titled my time travel books ‘The After Cilmeri Series’ because they tell the story of what happened ‘after Cilmeri’. Yeah. It’s obscure. If knew then what I know now, I would have called it something blander and more accessible like ‘The Children of Time series’. Too late now 😉