William Kent House is named after the Palladian architect who designed the house in two phases for Henry Pelham, Prime Minister between 1743-54. It is listed at Grade II* like its neighbour the Ritz Hotel, and is in the St. James’s Conservation Area overlooking Green Park. It was changed significantly by successive owners before ending up with a Napoléon III character overlain for Lord Wimborne. The 1970’s radical reordering of WKH for Eagle Star had reinstated a Kentian character during which many original features were discovered and restored. It retains both important historical and architectural interest, marking a transition at the end of Kent’s career, built two years before 44 Berkeley Square. The building is an important survival in the Palladian movement within west London – Kent lived with Lord Burlington on Piccadilly until shortly before his death, and also designed Devonshire House. William Kent House was bought by the hotel, 100 years after Cesar Ritz’s first attempt. Our brief was to add seamlessly the fine C18 rooms as function suites to the Mewès & Davis’s Louis XVième Hotel. The only possible connection to the Hotel’s ground floor enfilade was through a lightwell filled to the brim with plant. Staff also needed their own service connection between kitchens on the floor below. Another requirement was to connect the hotel bedroom corridor to the second floor of WKH, whose character was only suitable as suites. Three floors of plant had to be stripped out whilst maintaining both hotel and the Ritz Casino operations. Much plant was rationalised and replaced with more efficient equipment on the hotel roof. A new steel structure had to be inserted around the running Casino AHU two basements below. Besides the two storeys of links, it had to support the new plant without vibration or sound penetration to the public areas. A further layer of plant was added above the ground floor link, visually screened by louvres and leaving sufficient space for air circulation. Our task was to preserve the special character of both listed buildings as part of the conversion works. This involved extensive research and documentation. The interior design has followed the character and detail recorded in the inventory taken after Pelham’s death. Kent’s grisaille paintings in the Great Room ceiling, like all others, have been restored and regilded. Owen Jones’s fish-scale motifs, painted in the mid C19 to lighten the heavy bands, were reinstated to good effect – Kent resolved this problem two years later in 44 Berkeley Square. Damask wall coverings and carpets have been specially woven. During the investigation of dipping floors, inadequate storey-height trusses designed by Kent were discovered and had to be strengthened without loss of fabric. The restoration and change of use of William Kent House will once again allow it to become accessible to the public and used for important events for which it was originally designed.