Carved reliefs of wild boar, satyrs, griffons and goddesses were discovered mouldering beneath soil and leaf litter during the laborious landscaping of the garden of Villa Wolkonsky, which was once the home of a Russian princess.
As gardeners hacked through the tangled vegetation, they discovered more than 350 artefacts – far more than they had expected to find.
The marble statues and funerary reliefs, once covered in slime and moss, were cleaned by experts and went on display on Wednesday for the first time in the gardens of the villa, a historic palazzo which has been the residence of the British ambassador to Italy since the end of the Second World War.
They include stone reliefs from ancient Roman tombs that depict the faces of freed slaves, their wives and children, as well as carved friezes showing chariot races and the ritual sacrifice of bulls.
The three-year restoration of the 10-acre garden was led by Nina Prentice, a keen horticulturalist and the wife of the ambassador, Christopher Prentice.
“I was weeding from the age of two,” she told The Telegraph in the grounds of the residence, which are shaded by holm oak trees and palms.
Rather than delegate the project to embassy employees, she performed much of the back-breaking digging and clearing of overgrown shrubs herself.
Working methodically through the garden, which is enclosed on one side by the well-preserved remains of a 1st century AD aqueduct built by the Emperor Claudius, she came across the marble carvings.
Many of the artefacts came from a nearby Roman necropolis and were used to decorate the garden when it was owned in the early 19th century by Zenaida Wolkonsky, a Russian princess who entertained the likes of Gogol, Goethe, Stendhal and Sir Walter Scott.
Mrs Prentice found ancient sarcophagi used as plant pots and Roman capitols wedged underneath slabs of marble to form benches.
“Everything had slid into ruin and was covered in muck,” Mrs Prentice said, walking past a grotto in which Nikolai Gogol is believed to have composed part of Dead Souls, a classic of Russian literature.
“Every time we ventured into a different part of the garden, there would be another amazing statue. I just kept saying to myself, ‘I can’t believe it.’
“There were bits scattered all over the place so we had to match hands with arms and heads with bodies.”
Many of the pieces that were rediscovered are important from an artistic and archaeological point of view, experts said.
“There’s a sarcophagus with a lion’s head from the imperial period that is of very high quality,” said Prof Christopher Smith, the director of the British School at Rome, an archaeological institute.
Dr Dirk Booms, a curator from the British Museum, said: “The funerary relief showing five freed slaves and a child is very rare. They have Greek names, suggesting they were Greek slaves who were freed by their Roman owners. The collection is an important part of the story of Rome.”
After falling on hard times as a result of the Bolshevik Revolution of 1917, the Wolkonsky family sold the villa and its gardens to the German government, who used it as their embassy in Rome.
During the Nazi occupation of Rome in 1943 and 1944, its underground bomb shelter is thought to have been used to hold Italian civilians, some of whom were reportedly tortured by the Gestapo.
Others were shot when they tried to escape from the villa’s tennis court, where they had been temporarily held after a Gestapo sweep of the city.
The palazzo was confiscated from the Germans after the war and soon taken over by the British, who moved in after the existing British embassy was blown up by Irgun, the Zionist terrorist group fighting for a Jewish homeland, in 1946.
It later became the residence of the British ambassador, after the embassy was transferred to a modern, concrete building about a mile away in 1971.
The garden is to be opened for public tours twice a month.