Criminal Sentence 395: The Meaning of "The"

From a history book:

"Edward's great Abbey of Westminster became the spot where ... every monarch would be crowned except the 20th-century king, Edward VIII."

This sentence makes it appear that there was only one 20th-century king. Of course we know there were many. If you just delete the comma, all is fixed.

Let's see another example: "The 19th-century writer Charles Dickens wrote Oliver Twist." Dickens was one of many 19th-century writers. If he were the only one, we would have to write "The 19th-century writer, Charles Dickens, wrote Oliver Twist."