Pembrokeshire Deheubarth into Gwynedd. Norman/Flemish influence never fully recovered in West Wales. In 1138, the county of Pembrokeshire was named as a county palatine. Rhys ap Gruffydd, the son of Owain Gwynedd's daughter Gwenllian, re-established Welsh control over much of the region and threatened to retake all of Pembrokeshire, but died in 1197. After Deheubarth was split by a dynastic feud, Llywelyn the Great almost succeeded in retaking the region of Pembroke between 1216 and his death in 1240. In 1457, Henry Tudor was born at Pembroke Castle. He landed an army not far from his birthplace 28 years later in
Pembrokeshire to its proximity to the relatively warm Atlantic Ocean. Inland, average temperatures tend to fall 0.5 °C for each 100 metres increase in height. The air pollution rating of Pembrokeshire is "Good", the lowest rating. The rocks in the county were formed between 600 and 290 million years ago. More recent rock formations were eroded when sea levels rose 80 million years ago, at the end of the Cretaceous Period. Around 60 million years ago, the Pembrokeshire landmass emerged through a combination of uplift and falling sea levels; the youngest rocks, from the Carboniferous Period, contain the Pembrokeshire Coalfield. The