By a meticulously arranged coincidence, I am writing my last column for BD at the very moment that we are opening our first exhibition in the UK. In fact, the headquarters of the RIBA at Portland Place is seeing the second date of a travelling show that started last summer in the Venice Biennale and is now travelling via London to Russia, Brazil, Denmark and China.

The Banality of Good: Six Decades of New Towns, Architects, Money and Politics is its title and it tells the story of how new town planning in the 20th century became a global phenomenon, to which nations of nearly every ideological hue, using the same basic hierarchical diagram, added hundreds of towns, capitals, villages, even entire regions: from the pioneering English new town of Stevenage, through the postcolonial port city of Tema planned by Constantinos Doxiadis in Ghana, to the sprawling, state-planned Dutch suburb of Almere.

After that, however, we see how new towns disappeared from the centre of architectural attention where they had basked for 25 years. Seemingly under pressure of postmodernism, contextualism, general anti-technocratic relativism and of course the halting of industrial growth, new town planning became outmoded, nostalgic even, a quaint hold-over from the time we believed in Vorsprung durch Technik.

Actually — and this is the subject of three of the six triptychs on 20th century new towns in the exhibition — new towns are still being built, in greater quantities than ever before, using the same diagrams and structural forms as 30, 40 years ago, but to entirely different ends, with different parties involved, and with architects in a humiliatingly marginalised role.

Of course we know the Foster-autographed renderings of Masdar City, and the stream of unbuilt OMA master-plans, but right now new towns all over Russia and Asia are being built by international engineering consultancies, with money provided by equally footloose investment funds, in special economic zones cut out from national territories by regimes of a questionable political nature, for inhabitants who are either fearful ex-pats or local upper-middle classes who want to be protected from the grime of the masses living in the real cities.

It is interesting that a model developed by architects and planners, one that represented their most lofty ideals for how to provide an alternative for the city, were taken up by a post-war generation of nations as a tool to reorganise and sculpt society as a whole. It is tragic that it was abandoned by both public administrators and right-minded architects, and was then picked up from the roadside by a new generation of state capitalists, project developers and engineering consultants who used it to ends that are the polar opposite of the original.

Architecture and democratic politicians no longer “believe” in the state-sponsored masterplan as a way to reshape society. The private sector, however — without any democratic legitimacy or accountability — is now using this discarded part of our public design toolbox and filling in the huge gaps left by the public sector – and indeed the architectural profession.