Complex sentence: The castle was used by King Henry IV while on a sortie into Wales when he executed Llywelyn ap Gruffydd Fychan in the marketplace and later attacked by the forces of Owain Glyndŵr in 1403, and has stood as a ruin ever since.
Split into simpler sentences: The castle was used by King Henry IV while on a sortie into Wales when he executed Llywelyn ap Gruffydd Fychan in the marketplace. It was later attacked by the forces of Owain Glyndŵr in 1403, and has stood as a ruin ever since.