Anonymous art: the posters that inspired the uprising of 1968

The identity of the artists that created them is one of the great unsolved mysteries in the modern history of protest art, yet the body of work these anonymous designers produced remains one of the most powerful testaments to the revolutionary spirit of the age in which they worked.

Some 48 posters were knocked up in the factories and art schools of strife-torn France at the height of les événements urging students and workers to take to the barricades to paralyse Charles de Gaulle's ultra-conservative government with a series of strikes and demonstrations. They go on display at the Hayward Gallery later this month as part of a series of events marking the 40th anniversary of the uprisings that engulfed Europe in 1968.

The unique collection was assembled by the New York-based writer and curator Johan Kugelberg. Among the silkscreen works, hastily produced and plastered on walls and buildings, are posters urging students to support the factory workers and warning the public against ovine compliance with the ageing president's reactionary rule.

At the height of the turmoil, when students took over the École des Beaux Arts to form the Atelier Populaire, or Popular Workshop, the posters were described by student leaders as "weapons in the service of the struggle... an inseparable part of it".

Mr Kugelberg has spent the past decade painstakingly putting together his collection. He believes only 150 to 200 were ever produced during just a few weeks of that year.

"These are really, really rare," he said. "The problem you have is that you cannot go to Sotheby's or Christie's or look on eBay for them. They exist only in private collections, in suburban flea markets and can only be discovered through serious detective work."

The upheavals of 1968 caught the French ruling class by surprise. In his 1967 New Year's Eve message, de Gaulle believed his problems were behind him. "It is impossible to see how France today could be paralysed by crisis as she has been in the past," he said. But trouble was brewing across the world. In January 1968, the reforming Communist leader Alexander Dubcek took power in Prague, while a few weeks later the Tet offensive began against United States forces in Vietnam.

Deepening disquiet over the war spread beyond US campuses and cities, many of which were already feeling the impact of the growing civil rights movement.

In March there was violence when anti-war protesters surrounded the US embassy in London. Opposition to the war intensified across the world as reports of atrocities proliferated. By May Paris was alight.