Fifty years after the river Arno burst its banks with devastating consequences, Florence will this week remember the Angels of the Mud who came to save the Italian city's artistic treasures.

The army of cultural rescue volunteers came from all over and, half a century later, the events of November 4, 1966 and its aftermath still burn bright in the memory of Antonina Bargellini.

"There is not one Florentine who is not moved when the subject of the disaster comes up," recalls the 72-year-old, whose late father, Piero, was mayor of the city at the time.

"We were living in the neighbourhood around the Santa Croce church," she said. "I can remember being with my brothers and sisters watching the water come into our garden and then rising up to five metres high. We had a roaring river crashing against our doors."

Bargellini also recalls vividly her father being called away amid fears the city's fabled old bridge, the Ponte Vecchio, would crumble under the deluge, and the acts of kindness between neighbours without food, potable water or electricity.

"It was like in medieval days, information being circulated by word of mouth, door to door," she recalled.

- Priceless cultural heritage -

Two days later the waters receded, exposing vast meadows of mud, studded with debris and contaminated by heating fuel that had been stored in city centre cellars.

The flood had left 34 people dead, half of them in the city, the others in the surrounding countryside.

The water got everywhere, up to the first floor of town houses but also into every nook and cranny of churches, the central library and museums, causing immense damage to the city's priceless cultural heritage.

Despair however quickly gave way to a spontaneous outburst of offers to help, not just from locals but also from all over Italy and the rest of the world.

"Gli Angeli del Fango" (Angels of the Mud) they they came to be called, many of them young students brimming with the idealism and optimism of the time.

And hundreds of the estimated total of 10,000 volunteers are back in Florence this week to celebrate the anniversary of the disaster and their efforts to save irreplaceable books, paintings and other works of art.

"We want to remember them and thank all of them in order to commemorate an event that is part of the city's identity," said Dario Nardella, the current mayor of Florence.

- Four million books -

Among those due to join President Sergio Mattarella at a gala dinner in the Palazzo Vecchio on Friday is Susan Glasspool, a 71-year-old Englishwoman who met her future husband during the clean-up at the Academy of Fine Arts.

"I think all of us Angels of the Mud feel a lot of nostalgia for that time and I am curious to know if the others have had the opportunity to have that feeling of solidarity again," she told AFP.

Glasspool said the most moving moment of her time in Florence back then had been discovering a piece of the original wooden model of the cupola of Florence's cathedral.

Made in 1420 by renowned renaissance architect Filippo Brunelleschi, the model was put back together and is now on display in a city museum dedicated to the construction of the city's Duomo.

Over the course of the last 50 years, many of the 1,800 works of art and some four million books that were saved by the Angels of the Mud have been returned to their original settings.

But there are also numerous pieces still languishing in stores awaiting restoration or a display spot.

That is no longer the case for "The Last Supper", a giant tableau by Giorgio Vasari (1511-1574) that was submerged by the flood.

After 10 years of minutious restoration work, the painting will be returned to its rightful place in the Basilica of Santa Croce on Friday as a symbolic celebration of the contribution to the heritage of humanity made by the Angels of the Mud.