The importance of Hampstead Garden Suburb in the history of 20th Century architecture and town planning cannot be overestimated. The brainchild of Henrietta Barnett, the Suburb was to be a model community with people of all classes living together in beautiful houses set in a verdant landscape. Laid out by Raymond Unwin, with Edwin Lutyens, the houses and flats represent the best of English domestic architecture of the early twentieth century. Today, it is an environment of international significance. The eminent architectural historian, Sir Nikolaus Pevsner, described it as "the most nearly perfect example of that English invention and speciality, the garden suburb". The Hampstead Garden Suburb Trust was set up in 1968 "to do all things possible to maintain and preserve the present character and amenities" of Hampstead Garden Suburb. The Trust operates a Scheme of Management, which ensures that the architectural standards of the Suburb's founders are maintained. The Trust publishes policies for the protection of the character of the Suburb and householders must obtain the Trust's approval before making changes to the external appearance of their property.