From Caernarfon to Cardiff, why does Wales have so many castles?

Wales' historic monuments agency Cadw currently looks after about 100 castles.

But over the centuries hundreds have been built - the number of Norman castles alone could be around 600.

Among the most famous are the castles in Edward I's "ring of stone", including Beaumaris, Caernarfon, Conwy, Criccieth, Harlech and Flint.

The English civil war in the 1640s was effectively the last conflict where castles played a significant role - the great period of castle warfare stretched from medieval times to the 17th Century.