Question: which is the biggest p and o ship
[{'answer': 'Britannia', 'provenance': [{'wikipedia_id': '4761033', 'title': 'P&O Cruises', 'start_paragraph_id': 11, 'start_character': 435, 'end_paragraph_id': 11, 'end_character': 444, 'bleu_score': 1.0, 'section': 'Section::::History.:21st century.\n'}]}]