The Pool at London Marriott Hotel Regents Park
London Marriott Hotel Regents Park's pool is acknowledged by professionals. Out of 3 publications that we monitored, 3 acknowledged the pool, like Gayot, Oyster and Star Service.
London Marriott Hotel Regents Park 
Gayot
Oyster
Star Service
Gayot "Other hotel facilities include a large indoor pool, leisure club and health and beauty salon"
Oyster "The hotel has extensive meeting and event space, an Italian restaurant and bar, and wellness facilities like a gym, spa services, an indoor pool, and a sauna"
Star Service "Besides the exotically vaulted and enormous (for London) pool, the hotel offers a gym, sauna, solarium, hairstylist, and various health and beauty treatments"
