The Italian film-maker and author Lorenza Mazzetti, who has died aged 91, declared herself to be a genius on her first day at the Slade School of Fine Art in London, and she made good on her promise. She unleashed a capacity to tell stories in film and literature that evoked a childhood trauma in Italy that she found too painful to discuss in person. Living in Britain after the second world war, she became a founding member of the British Free Cinema movement alongside Lindsay Anderson, Karel Reisz and Tony Richardson.

Her most acclaimed movie, made in 1956 with the support of the BFI’s Experimental Film Fund, was Together, a heartbreaking depiction of urban isolation. In this largely dialogue-free film, the painter Michael Andrews and the sculptor Eduardo Paolozzi appear as two brothers, both deaf and without speech, working as dockers in the blitz-struck East End of London, who are snubbed and taunted by locals, with terrible consequences.

Mazzetti’s experiences as a stranger in London, and of her own close sibling bond with her twin sister, are beautifully expressed in this film, which was shot on eerily bomb-ravaged streets that evoke the psychological suffering of the vulnerable brothers.

Together had its premiere, alongside Anderson’s O Dreamland and Reisz and Richardson’s Momma Don’t Allow, at the National Film Theatre in London in February 1956 as part of a programme called Free Cinema. This was the genesis of a brief movement, an invigorating precursor to the kitchen-sink realism of the British New Wave in the 1960s.

Lorenza Mazzetti’s best known film was Together, 1956

Mazzetti and Anderson, who were close friends, collaborated on an accompanying manifesto. Their idea of cinema rejected expensive effects in favour of a documentary-style authenticity: “No film can be too personal,” they wrote. “The image speaks. Sound amplifies and comments. Size is irrelevant. Perfection is not an aim. An attitude means a style. A style means an attitude.”

Mazzetti was born in Rome, the daughter of Olga Liberati and Corrado Mazzetti. After her mother died, she and her sister Paola were raised on a farm in Tuscany, by an aunt who was married to Robert Einstein, a cousin of Albert. Mazzetti remembered her childhood as a happy one until the summer of 1944, when as the allied forces advanced, SS officers entered the farmhouse and killed the family, saving the twins only because they did not share the Jewish family name, and Robert, who was not at home. Overwhelmed, Robert took his own life a year later.

Mazzetti described this massacre in her award-winning novel The Sky Falls (1962), and its sequel, Rage (1963). The third part of this autobiographical trilogy, London Diaries, was published in 2014, and described her life after the war in Britain and her film-making.

In London in 1951, Mazzetti was working as a waitress and producing what she called “strange drawings”. Eager to pursue her art, she managed to circumvent the usual admissions process at the Slade, part of University College London.

Despite being told, as she remembered it, that she was ineligible on grounds of her nationality, she refused to take no for an answer. “Not knowing what to say,” she later recalled, “I blurt out: ‘I’m a genius’.” This granted her a meeting with the director of the school, William Coldstream, who accepted her on the strength of her drawings and perhaps also by her captivatingly blunt manner.

It was while studying at the Slade that Mazzetti “liberated” some film-making equipment from the UCL film society and set about producing a low-budget adaptation of Metamorphosis by Kafka, with her fellow student Andrews in the lead. She scrounged various props, settings and even supporting players from forays into Portobello Road market. According to Mazzetti’s account, when Coldstream discovered she had used the camera and lights without permission he told her that she was liable for criminal charges.

His solution was to screen the film, called K, for her fellow students – if they approved, she would be retroactively pardoned. Mazzetti was gratified not just by a round of applause, but by an offer from Denis Forman, director of the BFI, also in attendance. He asked: “Would you like to make a film without having to go to prison?” The result was Together, and it went on to win a special mention award at Cannes in 1956.

Mazzetti returned to Italy that summer, where she made more films, including I Cattivi Vanno in Paradiso (1959), and wrote her books. She lived for a period with the journalist Bruno Grieco and briefly wrote a column for the magazine Vie Nuove. She painted and, in the mid-70s, ran a puppet theatre for children in Rome. In 1974 she married Luigi Galletti, and after his death she lived for the rest of her life in Rome with Paola.

In 2016 a documentary celebrating her formidable body of work and eccentric charm, Because I am a Genius! Lorenza Mazzetti, premiered at the Venice film festival. In 2018 she was made an honorary fellow of UCL. “Finally,” she wrote in a thankyou note, “I have graduated!”

Mazzetti is survived by Paola.

Lorenza Mazzetti, film-maker and author, born 26 July 1928; died 4 January 2020