Question: when was the last steam train used in uk
[{'answer': '11 August 1968', 'provenance': [{'wikipedia_id': '16909735', 'title': 'Fifteen Guinea Special', 'start_paragraph_id': 1, 'start_character': 131, 'end_paragraph_id': 1, 'end_character': 145, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '16909735', 'title': 'Fifteen Guinea Special', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 473, 'bleu_score': 0.9757530668325981, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 934717348965339737}, 'section': 'Section::::Abstract.'}]}]