We found the castle tump eventually in the most beautiful setting beside the river. Couldn't resist photographing the tree as well.  There are the remains of two castles at Mathrafal, this one  which archaeologists think dates from the 8th or 9the century (the  tump being erected  in the 12th century). Both were the seats of the early Kings of Powys.  The first, earlier site was an Iron Age hill fort about half a mile away, now in the centre of a Woodland Trust wood.