In Warren Ellis' Crécy the main narrator, an English longbowman, rails against the Welsh repeatedly, arguing that the reason the English were able to take Wales is that the Welsh could not rally into a unified force.
He says: "You know how the English conquered Wales? One village at a time. Because no Welshman would run to the next village to warn them the English were coming. You all went down warm in the knowledge that the next village would get it too, and they deserved it for being foreign"
How accurate is this, if at all? Or is it simply rhetoric from a deeply xenophobic (and rather sweary) character?
Also, where might I read more about this topic and the rise of England in the British Isles?
FWIW, Crecy in general is not particularly historically accurate (the origin of the two-finger salute, for example, is apocryphal), and it wasn't Warren Ellis' goal to maximize historicity.
It's also worth understanding that it wasn't properly "English" people who conquered Wales, but men who would have considered themselves Normans, at least at the outset. Indeed, it was King Gruffydd ad Llywelyn who actually began harrying and attacking Norman positions in England, which forced the Normans, under William the Conqueror, to invade Wales. The Welsh consciously provoked the English, in other words, it was not a spontaneous English invasion that no Welshmen knew about -- and therefore the idea that Welshmen weren't "running to the next village to warn" each other is almost certainly poppycock, since most Welshmen would have known what was going on.
By the reign of William II, most of Wales was under the control of the Normans, but this didn't last. It's again, rather inaccurate to portray the English as easily taking over Wales, because the Welsh were quite successful against a series of Norman-English invasions under Henry I and King Stephen (who were now beginning to consider themselves English, rather than just Norman/French, at least to some degree).
Later, under Henry II, the Welsh demolished English/Norman armies at the Battle of Ewloe in 1157. Almost killed and totally routed, Henry retreated. He made another attempt to invade Wales in 1163-65 where he was again met with devastating defeat at the Battle of Crogen.
It wasn't until a century later, under Edward I (now a proper English king), called "the Longshanks," that Wales was finally conquered. While it's true that at this time a large part of Wales was divided into separate principalities with some infighting, they were, to a certain extent, united (i.e., vassalized) under the largest principality, Gwynedd. It's also important to remember that some districts of Wales were still under Anglo-Norman control, and that these consciously assisted the English invasion (perhaps this is the origin of Ellis' claim that the Welsh didn't warn each other).
In no sense were the Welsh fighting each other or divided in this war against English invaders. Rees Davies, in Law and National Identity in Thirteenth Century Wales states that there was almost universal support for the war effort amongst the Welsh people, who were coordinated and enthusiastic. The Welsh people, according to Davies, saw this war as an illegal attempt by Edward to impose English laws on Wales, which they soundly opposed.
The truth is that Edward won because he had better troops and more of them, and because he had some luck -- but by no means did he win every battle. At first, he was defeated at Llandeilo Fawr, or more properly, his vassal the Earl of Gloucester was defeated there. Then, during a peace negotiation, Edward's commander Luke de Tany tried to carry out a surprise attack on the Welsh using pontoon bridges (pretty dirty stuff), but was defeated.
What turned the tide was that somehow Edward was able to goad or lure the Prince of Wales (the real one, not the son of the king of England) Llewelyn ap Guffudd (literally "The Last Llewelyn") to come out of his stronghold and fight. He was killed at the Battle of Orewein Bridge, which dealt a death blow to the Welsh cause (and was a very lucky turn of events for Edward).
From here, Edward raised a new army and pushed into a Wales in chaos, and then completed his takeover. But nowhere do the history books suggest that Welshmen weren't working together, and weren't warning themselves/fighting hard.
Sources:
EDIT: Thanks to /u/TheGreenReaper7 for pointing out some screwups above. Corrected. Please reference his comment, below for further clarifications.