The second project is Nagel House, a design they developed together for an art and architecture competition in Zurich. Instead of adopting the repertoire of landscape architecture, urban furnishing and paving patterns – and, most crucially, avoiding anything that resembled a public-art project – the three decided to construct a replica of a famous Chinese house that withstood the demolition process until it found itself sitting precariously on a scrap of land, before then being destroyed. Were this “stubborn nail” to reappear in the centre of Zurich, it would be underneath the large reinforced-concrete viaduct across Escher-Wiss-Platz.

The idea of turning it into a Chinese restaurant and hanging paper lampshades from the viaduct soffit lent substance to their clear strategy. Although approved and paid for, the project was never completed because those opposing it played their cards well on the table of bureaucracy and the media. It was then buried once and for all by a referendum, although lost by the narrowest of margins.

The complexity of the exhibition starts to become apparent in the adjacent room, during a two-hour conversation chaired by the influential and soft-spoken Italian curator Mario Codognato.

Despite featuring different types of collaboration, all three projects challenge architecture’s claim to lend form to a space precisely when they do so very successfully. It is important not to misconstrue this point: it is precisely because Caruso and St John’s work is so specific and of such good quality that the dilemma emerges in all its, almost philosophical, clarity.

First, there is the issue of exhibition design. Adam Caruso told the story of their exchanges, which commenced with a request from Thomas Demand to solve the problem of the exhibition at the Fondation Cartier – once again, a transparent building and the risk of being relegated to the basement. Problem Solving is the title of a short text by the architect that can be read on the walls of the Rome exhibition.

It is far from being an indication of false modesty and, more often than not, the problem to be solved is an absence of “space”. So, the richly decorated and “untouchable” rooms of Palazzo Pitti prompted the construction of outsize pieces of furniture to be used as exhibition devices. In Zumthor’s Kunsthaus in Bregenz, the curtains were moved to form an enclosure within the open space of the gallery.

During the conversation, Demand complains that architects (in general but not the one sitting beside him) see artworks as objects in a room and not as ideas so Caruso and St John’s ability to find a solution without resorting to conventional architectural features may be the reason for working together. To use the artist’s words: “I stopped pondering and just let them do their part. Results were mostly baffling and I kept thinking a good while about them, even if I believe I got the proposition right away.”

Last come Nagel House and its “clever move” on the chessboard of public space. This proposal, while questioning the arrogance of architecture and conventional public-art practices, actually managed to create even greater friction. Does the absence of a sense of humour in Swiss right-wing populist party explains the defeat of this intelligent project? You have to visualise it, constructed and after some time has passed. The unusual lie of the house beneath the viaduct would suggest to passers-by not familiar with the story that, in some generic way, the house preceded the infrastructure, as was the case in the original Chinese reference.

Italy abounds, often unintentionally, with such situations. Not far from the British School, the site of the MAXXI museum designed by Zaha Hadid was created in 1998 by casually separating two army barracks, but a house inhabited by stubborn Italian-army residents remains trapped within the museum shell. This may seem a parallel of Nagel House and a perfectly successful one, because not designed. Architecture is very present as a discipline in this partnership, precisely because of its absence.