Question: when was bse first observed in great britain
[{'answer': '1986', 'provenance': [{'wikipedia_id': '19344418', 'title': 'Bovine spongiform encephalopathy', 'start_paragraph_id': 4, 'start_character': 130, 'end_paragraph_id': 4, 'end_character': 134, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19344418', 'title': 'Bovine spongiform encephalopathy', 'start_paragraph_id': 49, 'start_character': 0, 'end_paragraph_id': 49, 'end_character': 1049, 'bleu_score': 0.988538208695211, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 14537204896874515685}, 'section': 'Section::::Epidemiology.:Europe.\n'}]}]