Question: when did the vikings first reach the shores of britain
[{'answer': '793', 'provenance': [{'wikipedia_id': '31581503', 'title': 'Norse activity in the British Isles', 'start_paragraph_id': 3, 'start_character': 150, 'end_paragraph_id': 3, 'end_character': 153, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '31581503', 'title': 'Norse activity in the British Isles', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 387, 'bleu_score': 0.9098786243711551, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16045871119608197218}, 'section': 'Section::::Abstract.'}]}]