One of London's best restaurants is a hidden gem in the venerable National Gallery of Art, where you'll get your food and art on. The National Dining Rooms have won awards and serve local, seasonal fare (like lamb fillet & sweet corn salsa, or oak-smoked salmon).
You'll also savor gorgeous artwork in a gorgeous art gallery (free!)
The National Gallery of Art, London
Van Gogh "Sunflowers"
JMW Turner "The Fighting Temeraire"
Botticelli "Mystic Nativity"
(Images, top to bottom, via National Gallery Dining Rooms and Venere; all art images from National Gallery of Art via The Art Wolf, The Mail Online, and Olga's Gallery).