With the megabuild shell nearing completion, the hotel turns its attention to the interiors, employing some of the world's top designers and craftsmen to meet the expectations of their well-heeled guests. A highlight is the new penthouse. With a rumoured £100,000 per night price tag, it will span the entire rooftop of Claridge's and feature four bedrooms, a swimming pool and its own lake. Its look is the vision of renowned Parisian interior designer Rémi Tessier, who is determined to use only the rarest materials and has suppliers quaking under the pressure of his high demands.Meanwhile, down in the basement, Claridge's first-ever spa is taking shape under the guidance of Inge Theron, who aims to combine imported scents from Kyoto in Japan with the latest skincare tech to provide an unrivalled experience. But she faces plenty of unexpected challenges. First there is the noise from tube lines that requires a rethink on the build and then, just weeks from opening, unprecedented levels of rainfall in central London cause the basement to flood and destroy much of what her team have been working towards.If they can get the spa back on track, David Walliams is keen to take the inaugural dip in the hotel's first-ever pool, while on the roof, the last minute addition of a piano pavilion prompts a very special guest to do an exclusive, impromptu festive performance, just as the penthouse is ready to start welcoming its first overnight guests.