This purpose-built extension to a Grade II-listed Mayfair mansion houses an extensive private antiques collection under an automated sliding glass roof. Centred around an oversized custom-made fireplace with unique motif symbols, the exclusive collections are housed in weathered mild-steel riveted display cabinets with integrated lighting, to form seamless walls of exhibits. An extensive library covers one entire wall, adorned by a centred oversized custom-made Georgian inspired convex mirror. Building in such a tight location in the Grosvenor Estate conservation area created an interesting technical and logistical challenge, which was successfully overcome to create a bespoke collectors den with filtered daylight throughout.