Question: when did the slave trade end in britain
[{'answer': '1833', 'provenance': [{'wikipedia_id': '1811656', 'title': 'Slavery Abolition Act 1833', 'start_paragraph_id': 0, 'start_character': 22, 'end_paragraph_id': 0, 'end_character': 26, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]