He was a concentration camp survivor who settled down to postwar life in Hungary as a modest butcher who occasionally indulged his poorer customers with giveaways.

But István Kövesi was also something of a secret art collector who over the years poured his money into more than 200 paintings by some of Hungary's national treasures. In an echo of the recent case in Munich where more than 1,000 works of art were rediscovered most of the Kövesi collection has been unseen for up to 50 years. "As regards 'flat collections', this is one of the greatest," the art historian Péter Molnos said.

Now his daughter has consented to show the works by artists such as József Rippl-Rónai, János Vaszary and Izsák Perlmutter.

But in some senses it is the backstory to the collection that is almost as compelling as the works themselves.

Detail from Sándor Bortnyik's Suburban Landscape, 1928, from the Kövesi collection. The Hungarian butcher knew the painter personally

A mischievous child, Kövesi was expelled from school aged 14. In the second world war he survived enforced labour programmes and Mauthausen concentration camp, returning home the sole survivor of his family, barely five stone and infected with typhoid.

He married a woman who had seen Dr Mengele pick his two sisters out of a line to be killed at Auschwitz. They had two children and established a butcher's shop and a small farm before fleeing to Budapest from the enforced Soviet nationalisation in 1949. He spent years working 16-hour factory shifts cleaning oil containers until history intervened again with the Hungarian Revolution in 1956. He took over the shop of a butcher who fled the country.

He diversified into pickling and was soon one of the district's most popular vendors. The political situation precluded the buying of extra properties or big cars, so Kövesi's first steps into the art world were motivated by financial practicality – but he quickly fell in love with paintings.

Outside of the state auction house BÁV, his main adviser was an art historian friend, Mrs Sándor Kapolcsi, who would identify forgeries from private dealers's caches, and be slipped steaks as commission. "Good quality meat was very hard to find in socialist times, so this was perhaps the biggest weapon in his armoury," Molnos said.

Kövesi's most valued adviser at the BÁV was art historian Katalin Sinkó, who described "Uncle Kövesi" as atypical "because he asked the opinions and advice of art historians and his fellow collectors. He would embrace me and charmingly ask 'Katika, you have such good taste, what is your opinion about this painting?'"

Despite Kövesi's proclivity for cheerful paintings, the collection also documents human stories with the opposite trajectory of his own life. For example one painting, Kis Cleo, depicts Perlmutter's muse and adopted daughter, who had married a Persian prince and inherited 60 Andrássy út, an address that recent visitors to Budapest may better know as the Terror House museum. From a Jewish family, but politically naïve, she rented out part of the building to the fascist Arrow Cross party, who made it their "House of Loyalty" headquarters. After the war it was taken over by the ÁVH secret police. Cleo was sent to the provinces to work as a day labourer until her death.

As Hungary sleepwalked through the 1970s, Kövesi's life once again echoed the times, as he withdrew into family life and the domestic idyll he had created at home. "He always told his children to protect the collection – of course keeping it secret was very important in the socialist era," Molnos said.

Since his death in 1981, Kövesi's daughter has wrestled with whether to keep the collection out of sight or to celebrate the life of her beloved father. Fortunately for art lovers, she has decided on the latter course. However when the exhibition closes in March this unique collection will disappear from public view once again. It is certainly not for sale.