When Thierry Noir moved to west Berlin in the early 1980s, he found himself living next to the Wall, a menacing and at the time dreary three-metre barrier dividing the two halves of the city. “It was a melancholic place, day by day, nothing happened really. That life was putting me in a kind of isolation, and I began to think, I have to resist that because I am going crazy. So I had a need to paint the wall, just to do something against it.”

More than four decades after the Frenchman became one of the first artists to paint the infamous barrier, he is preparing to decorate another section of wall in Britain to mark next month’s 30th anniversary of its fall. He and Stik, a London-based street artist who paints often enormous, expressive stick figures, will paint and install two original sections of the wall, which for a month will greet visitors outside the Imperial War Museum in south London.

But while the three-metre slabs of reinforced concrete have become museum pieces or lucrative collectors’ items, Noir has cautioned younger generations not to be complacent about the freedoms that he and others assumed the fall of the Wall would usher in.

“Thirty years ago, we were thinking, ‘Oh, it’s freedom on Earth, everything will be better now,” he told the Guardian. “But it’s not, it’s the opposite. In 30 years, many, many walls have gone up since. This is a message to the young generation: do not repeat the mistakes of your parents.”

When he first started painting, Noir said Berliners were shocked and suspicious. “My neighbours asked me a lot of questions: who gave you the money for this? Are you a spy from France?” So persistent were those challenging him, he said, that he changed his style of painting “so it was possible to talk and paint at the same time”, developing an instantly recognisable motif of “big heads, three colours and black lines all around” that came to be synonymous with the Wall itself.

Facebook Twitter Pinterest Thierry Noir repainting part of the original Berlin Wall in 2009 outside the Wende Museum in Los Angeles. Photograph: Nick Ut/AP

Others quickly began to paint alongside him, and by the time the Wall was breached on the night of 9 November 1989, long stretches of the barrier were covered in vibrant protest images. Did the art itself help to usher in its fall? “I think so,” says Noir, “because the special art on borders helps to [highlight] that border, and to say, ‘This is not normal to have this in our country.’” It was, he says, “a mutation of art”.

Walls are frequently called something else these days, he notes: “It’s not a wall, it’s a peace border or a green line. They have new names to sell the separation to the population, to try to minimise their effect. But when some border artists come and say, here we are, boom boom boom, the government have to explain why there is suddenly 200 metres of art in the middle of the city.”

The two artists have collaborated previously. Paris Agar, an art curator in IWM’s cold war team, said bringing them together on the project would “marry the beginnings of street art’s association with the Berlin Wall with contemporary street art as it responds to issues in today’s society”.

The two decorated slabs will stand at the museum’s entrance, close to another original section of wall that is in its permanent collection, she said.

Younger people with no memory of the cold war might think “not again, same old same old”, said Noir, “But take care. It might come back, and this time be really serious.

“That is why I think that those pieces of the Berlin Wall [that survive] are a symbol of the new freedom in Europe, but [we must] tell the young generation that that freedom was not falling from the sky. It was a big fight to get that freedom. And do not forget that.”

• The sections of wall will be on display at IWM London between 5 November and 1 December 2019