Possible Clues:

• Uncovered king given check where there's a castle
• Men of —, song
• Welsh castle
• Welsh castle town
• Town with a castle near Barmouth
• Welsh town with well-known castle
• Charles did not finish being upset in front of first historic castle
• Castle in Snowdonia
• Outsiders snubbed by king going to church in Welsh town
• King ignoring outsiders initially constructed his castle here