This historical episode is recounted in a comic strip, "Maison du peuple 65", which comes out on Friday. The album tells in the form of a detective story how the majestic headquarters of the Belgian Workers' Party (ancestor of the PS), built by Horta between 1896 and 1898, fell victim to real estate speculation in the midst of the economic boom of the Trente Glorieuses.
"Weakly defended" by the party that occupied it, the subject of developments criticized by the architect himself, the Art Nouveau building with its metal structures and undulating forms typical of the style seemed, from the 60s, to belong to the past.
And a safeguard motion voted on at an international congress of architects in Italy in 1964 - the "Venice Charter" - did not allow the fate of the "People's House" to be reversed.
The building was demolished in 1965 and was never rebuilt, although there was initially talk of "reassembling" it in another location, thanks to the numbering of the main stones and ironwork pieces.
It was replaced a few years later by a 26-storey concrete skyscraper in the historic Sablon district.
With a fictional plot in a very real setting and context, the comic strip, written by historian Patrick Weber and cartoonist Baudouin Deville, echoes the regrets that Belgians may express in the face of "Bruxellisation", a term describing the upheaval of the urban landscape at that time.
Against the backdrop of the inertia of the political power, which "was not aware of the value" of the People's House, underlines Baudouin Deville.
"No one prevented us from destroying an incredible architectural achievement," adds Nicolas Anspach, head of the eponymous publishing house.
Today, the work of Victor Horta, four of whose major residences in Brussels are listed as UNESCO world heritage sites, is one of the major tourist attractions of the Belgian capital.
The album is the sixth in a series initiated in 2018 by Anspach and which aims to be a visual fresco of the history of Belgium, focusing on a few key places and dates.
The title is always accompanied by the last two digits of a year, since the first issue, "Sourire 58", which celebrated the Universal Expo and the Atomium, another symbol of Brussels, against the backdrop of a spy affair.
Common to each episode: a red-haired heroine, Kathleen, who became an investigative journalist after having been a hostess at the 1958 Expo, and who, like Tintin, never ages.
"Taking history as fertile ground for invention is nothing new," notes Patrick Weber. "The idea is to revisit the common memory, to resurrect parts of Brussels that may have disappeared from the landscape but are still present in people's minds."