Question: when was the tower of london first built
[{'answer': '1078', 'provenance': [{'wikipedia_id': '31165', 'title': 'Tower of London', 'start_paragraph_id': 1, 'start_character': 523, 'end_paragraph_id': 1, 'end_character': 527, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]