A rare jewel sits in the middle of the Hyde Park Corner roundabout. The Quadrant Gallery, run by English Heritage, occupies the Wellington Arch. The gallery is showing a series of exhibitions to mark the centenary of the 1913 Ancient Monuments Act, a landmark in conservation. The present show (until 15 September) examines efforts to protect Georgian Britain during the early 20th century.

The Luftwaffe (see Holland House library after an air raid, 1940, above) was nothing compared to rapacious British developers. Photographs show sledgehammers being taken to Adelphi Terrace, from which Robert Adams’s striking doorframe was salvaged.

The title, Pride and Prejudice: The Battle for Betjeman’s Britain, is misleading for Betjeman was not the only famous member of the Georgian Group, which led the conservation effort. A petition records the interest of Sitwells, Sackville-Wests and Byrons. Yet this was not an elite operation. The most touching exhibits are a string of frankly ordinary watercolours that were commissioned to depict vanishing provincial England.

The exhibition also charts parliament’s changing attitude to our heritage. It opens in 1914 at 75 Dean Street, site of the first attempt at a Preservation Order under the 1913 Act. MPs rejected the application and upheld the property owner’s rights. The show ends with the introduction of statutory listing in 1944, under which the house, with its elegant façade and rare painted hall, would have been protected. It’s now a functional brick-faced building, home to a TV company.