Question: what is the main catholic church in london
[{'answer': 'Westminster Cathedral', 'provenance': [{'wikipedia_id': '391897', 'title': 'Westminster Cathedral', 'start_paragraph_id': 0, 'start_character': 0, 'end_paragraph_id': 0, 'end_character': 21, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]