Question: when did the metric system start in uk
[{'answer': 'mid 1960s'}, {'provenance': [{'wikipedia_id': '2732151', 'title': 'Metrication in the United Kingdom', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 1009, 'bleu_score': 0.9654391690111981, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3621205075031968901}, 'section': 'Section::::Abstract.'}]}]