Question: when was the first underground railway (metro railway) started
[{'answer': '1863', 'provenance': [{'wikipedia_id': '17839', 'title': 'London Underground', 'start_paragraph_id': 2, 'start_character': 128, 'end_paragraph_id': 2, 'end_character': 132, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '17839', 'title': 'London Underground', 'start_paragraph_id': 2, 'start_character': 35, 'end_paragraph_id': 2, 'end_character': 547, 'bleu_score': 0.785771059366778, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5154750662873697951}, 'section': 'Section::::Abstract.'}]}]