More than 200 architects from around the world have joined heritage groups in a last-ditch campaign against the £12 million redevelopment of Belfast’s landmark Ulster Museum. The scheme by Hamilton Architects— which has planning permission — aims to redevelop the B+ listed, Francis Pym-designed brutalist extension at the 1920s museum with 1,225sq m of extra space, including a large glass entrance facade. But the Ulster Heritage Society, which argues that the proposal would “seriously threaten [the building’s] value”, has revealed that a petition against it has been backed by architects including John Tuomey and Barrie Todd, plus groups such as the Twentieth Century Society and modern movement lobbyist Docomomo. Rita Harkin, research officer at the UHS, said the campaign was a “last-gasp attempt” to persuade ministers to intervene.