A few MPs flouted a ban on taking photos inside Parliament this week, as they tweeted about the Brexit vote. Kelly Grovier finds echoes in an 18th-Century painting of a Masonic lodge.

Some rituals are never meant to be seen. So jealously guarded is the air in which these ceremonies are conducted, only the lungs of initiates are permitted to inhale it. None may breathe a word to the outside world. Perhaps the most famous such sacrament is the papal conclave: the congregation of cardinals that convenes in the Sistine Chapel whenever it is time to elect a new pope. The world has come to accept that the only whisper that will ever escape the tight-lipped confab is the skein of white smoke (or fumata bianca) it releases when it adjourns and burns the cardinals’ ballots, silently signalling that a selection has been made.

While awaiting the results on Tuesday night of a very different kind of momentous vote – whether the UK’s Parliament would accept Prime Minister Theresa May’s deal for withdrawing the country from the European Union – many around the world were surprised to discover just how secretive are the rites and conventions of the modern-day Palace of Westminster. It turns out that it too has esoteric customs kept from the untrained eyes of the public. Customs like the act of voting – which means walking. To vote on legislation, members do not cast ballots, tick boxes, press buttons, or pull levers. Instead, they merely stroll through one of two rooms, either the ‘Aye’ or the ‘No’ lobby, while the traffic through each is tallied.

Ordinarily, this curious custom is performed in privacy – publishing photos taken in these spaces is generally banned on security grounds. The outside world is none the wiser whether a given MP’s vote was delivered with a sprightly shuffle, a furtive lurch, or a splatter of mustard on his or her lapel. But these are not ordinary times. The matter at hand was the most fiercely debated issue in living memory. Patience with such outmoded traditions as secret strolls through ancient chambers to register one’s vote had begun to wear thin.

Labour MP Debbie Abrahams snapped the No lobby in Parliament on the night of the Brexit vote (Credit: Debbie Abrahams/Twitter)

Labour MP Debbie Abrahams snapped the No lobby in Parliament on the night of the Brexit vote (Credit: Debbie Abrahams/Twitter)

Ignoring the rules that ban the use of cameras in the Commons, several MPs took it upon themselves to capture the voting ritual in mid-stride as an unprecedented crush of parliamentarians, including over 100 rebels from May’s own party, jammed the ‘No Lobby’ to deliver a crushing blow to her agenda – the heaviest defeat that any UK government has ever suffered. Posting their illicit snaps to Twitter, they seemed eager to shine a light not only on a memorable moment in political history, but on the antiquated pageantry with which that moment is quaintly cloaked.

Scottish National Party member Pete Wishart captioned his snap with the exasperated assertion, “The utter, utter stupidity of how we vote in the House of Commons.” A photo by Labour MP Debbie Abrahams of the same ceremonial saunter by MPs, bathed in a timeless amber glow, manages to transmute the moment into instant nostalgia. The warm glimmer of Abrahams’s photo, which may come visually to define the extraordinary vote, has the air of something past or passing, an era coming to an end, a feeling amplified by the momentum of figures pushing forward but to what? – a future whose contours no one can divine.

A meeting of a Viennese Masonic lodge by Ignaz Unterberger (Credit: Wikimedia)

A meeting of a Viennese Masonic lodge by Ignaz Unterberger (Credit: Wikimedia)

The ambience of Abrahams’s smartphone snap, which offers us a glimpse into a hidden realm of abstruse practices, recalls a painting by the Italian-born 18th-Century artist Ignaz Unterberger, which captures a moment from a meeting of a Viennese Masonic lodge. Whether Unterberger’s disclosure of the lodge’s interior and some semblance of its famously secretive inner workings (an initiation involving swords and blindfolds and strange handshakes appears to be unfolding in the foreground) was authorised by officials of the chapter, to which he likely belonged, is unclear.

The contention by some that the painting depicts Mozart (seated on the far right) perhaps beside the librettist, Emanuel Schikaneder, with whom the composer collaborated on the opera The Magic Flute (which itself has been accused of divulging Masonic ciphers and codes), has been challenged by others. Whatever the precise drama or dramatis personae captured by Unterberger in his painting might be, it represents a momentary crack in the seal of secrecy that enshrined the cloistered order. Things were changing. The painting mystically demarcates the end of one era and the start of something new, if unknowable. Sometimes images do that.

If you would like to comment on this story or anything else you have seen on BBC Culture, head over to our Facebook page or message us on Twitter.

And if you liked this story, sign up for the weekly bbc.com features newsletter, called “If You Only Read 6 Things This Week”. A handpicked selection of stories from BBC Future, Earth, Culture, Capital and Travel, delivered to your inbox every Friday.