Anyone who finds themselves in Prague over the next few days – perhaps to attend the fabled Christmas market which dominates Staromestske Namesti (Old Town Square) in December – may notice that part of the city is missing. Not in the little lanes of the Czech capital's medieval core, but on the opposite side of the River Vltava – where the cobbled Velkoprevorske Namesti is one of the loveliest plazas in the elegant Mala Strana district.

Since 1980, it has been home to the "Lennon Wall" – a giant swirl of graffiti daubed across the rear flank of the Grand Priory of the Knights of Malta. This was born in response to the former Beatle's murder, but quickly became a canvas for youthful rage at life in communist Czechoslovakia – daubings of discontent fanning out around an image of Lennon in full saintly mode: long-haired, bespectacled, gazing out with piercing intensity.

The communist authorities were not exactly fond of this anti-establishment bulletin board, and covered it over on a regular basis. But in the 25 years since the Velvet Revolution – which prised open the Iron Curtain in Prague in November 1989 – the wall has been allowed to thrive, becoming a bloom of colours, shapes, scrawls and signatures.

At least, that was the case until last month, when, on the quarter-century anniversary of the revolution, concealing brushes were again at work. This time, however, the hands wielding them belonged to a group of students calling themselves Prague Services. Their plan, they say, was not to vandalise, but to break with the past. "Twenty-five years ago, one big totalitarian wall fell," read a statement. "Students of art are expressing their commemoration [of 1989] and opening room for new messages of the current generation."

They have a point. I stood in front of the Lennon Wall earlier this year – or as close as I could stand amid the 100 or so bodies milling in front of it. It had become something of an eyesore, not so much a framework for protest as a place to scratch the message "José 4 Yasmina, Praha 2014". And the only evidence of provocation was in the visibly annoyed expressions of the staff at the French Embassy, directly opposite – trying to thread their cars through the latest phalanx of excitable teenagers posing for selfies on their doorstep.

The Lennon Wall had achieved its destiny; arriving in an era of censorship and seeing the city through to a time when self-expression can be as glib as a smartphone photo. This evolution was underlined by the white-washers, who printed the Lennon-referencing comment "Wall Is Over" on their handiwork. The truth is that the spirit of demonstration is alive in Prague – current president Milos Zeman, who has been making pro-Russia noises in reference to the crisis in Ukraine, was pelted with eggs at a recent event to salute the revolution. But the Lennon Wall, having served its initial purpose, should be considered a fragment of yesteryear. "Imagine all the people, living for today," as the man himself sang.