On the 35rh and 36th floors of One Casson Square, part of the Southbank Place development, this penthouse has three bedrooms, interiors designed by Portia Fox and views of he London Eye and Houses of Parliament. it covers 3,100 sq ft, has a spiral staircase and floor-to-ceiling triple-glazed windows. The owners have access to a health club and spa with a £25m pool.