Question: when did big brother start on channel 5
[{'answer': '18 August 2011', 'provenance': [{'wikipedia_id': '861172', 'title': 'Big Brother (British TV series)', 'start_paragraph_id': 1, 'start_character': 997, 'end_paragraph_id': 1, 'end_character': 1011, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '861172', 'title': 'Big Brother (British TV series)', 'start_paragraph_id': 10, 'start_character': 0, 'end_paragraph_id': 10, 'end_character': 2219, 'bleu_score': 0.9637443355817131, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 11505464660862138786}, 'section': 'Section::::History.:Main series.:Channel 5 (2011–2018).\n'}]}]