Read this: In the floor, just inside the great west door, in the centre of the nave, is the tomb of The Unknown Warrior, an unidentified British soldier killed on a European battlefield during the First World War. He was buried in the abbey on 11 November 1920. This grave is the only one in the abbey on which it is forbidden to walk.[citation needed]
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): When was The Unknown Warrior buried?
11 November 1920