Question: when was national minimum wage introduced in uk
[{'answer': '1 April 1999', 'provenance': [{'wikipedia_id': '1127188', 'title': 'National Minimum Wage Act 1998', 'start_paragraph_id': 2, 'start_character': 158, 'end_paragraph_id': 2, 'end_character': 170, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1127188', 'title': 'National Minimum Wage Act 1998', 'start_paragraph_id': 2, 'start_character': 109, 'end_paragraph_id': 2, 'end_character': 496, 'bleu_score': 0.761528518872006, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8687713303943881078}, 'section': 'Section::::Abstract.'}]}]