Clarence House is the home of Charles, Prince of Wales in London. It is part of St James's Palace, and is on The Mall, close to Buckingham Palace (The Queen's home).
The Prince of Wales lives with his wife, Camilla, Duchess of Cornwall there. The Prince of Wales' offices and staff are also based at Clarence House, and any announcements made by his staff are attributed to "Clarence House" as an entity, just like announcements from The Queen are said to be made by "Buckingham Palace".
Prince Charles has lived at Clarence House since 2003. The Queen Mother lived at Clarence House from 1953 (the year after the death of her husband (King George VI)) until 2002, when she died.
51°30′14″N 0°08′21″W / 51.50389°N 0.13917°W