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 <answer>11 November 1920</answer>. This grave is the only one in the abbey on which it is forbidden to walk.[citation needed]
When was The Unknown Warrior buried?
11 November 1920