Warren Davies and his sister were walking home from school one evening to their home in Freystrop, where they lived with their grandparents. They had to cross a field and then a wood on their way, and had been taking this route for some time.
As they neared the end of the wood, they saw a bright yellow object, about the size of a bicycle wheel, which they thought at first was a balloon. It was floating amongst the trees and was moving backwards and forwards like a pendulum, about six feet each way.
The children wer scared and ran home. Although they continued to use the same route to school they were usually accompanied through the wood by their grandfather after this episode.
Source: The Dyfed Enigma Randall Jones-Pugh and F. W. Holiday 1979 page 58.