Greek prime minister asks Boris Johnson to return Parthenon marbles

London -- U.K. Prime Minister Boris Johnson commented in a meeting Tuesday with Greek Prime Minister Kyriakos Mitsotakis that the decision to return the famous Parthenon marbles to Greece would be left to the British Museum, rather than coming from Downing Street.

This is a break from his previous comments to Greek newspaper Ta Nea in March, when Johnson said the marbles shouldn't be sent back as they'd been "legally acquired" at the beginning of the 19th century.

The marble sculptures are part of a Frieze previously wrapped around the walls of the Parthenon, which represents the procession of the Panathenaic festival, a commemoration of the birthday of the goddess Athena. Built 442 to 438 BC by the great Greek sculptor Phidias, the Frieze is composed on 115 marble panels, adorned with carved reliefs that represent humans, divine figures, mythological creatures and animals honoring Athena.

In 1801, while Greece was under the rule of the Ottoman Empire, several of these blocks were taken by Thomas Bruce, the lord of Elgin, who was then the British ambassador to Constantinople. According to the museum's website, "Elgin's workmen cut off with saws or crowbars only the faces of the blocks that bore the relief decoration."

Elgin claimed he had secured a permit from the then Sultan of the Ottoman Empire, Selim III, a fact still disputed -- some say his permit only allowed for conducting research on the site.

"He secured a permit from the Sultan to conduct research on the Acropolis which was under Ottoman-Turkish rule. However, he did not limit himself to that, but went ahead and removed numerous sculptures," according to the Acropolis museum website, which says the sculptures were "forcibly removed" and "looted."

Upon Elgin's return to Britain, the pieces where moved to the British Museum, where they've remained.

"His actions were thoroughly investigated by a Parliamentary Select Committee in 1816 and found to be entirely legal, prior to the sculptures entering the collection of the British Museum by Act of Parliament," says the British Museum's website.

A large part of the Parthenon already had been destroyed in 1687, during a bombardment orchestrated by the Venetian army of Francesco Morosini against the Ottomans. The temple continued deteriorating until 2009, when the Acropolis museum was built at the foot of the monument, and all the marbles were transferred there for safekeeping.

While most of the remaining marbles are divided between the British Museum and the Acropolis Museum, some fragments can be found at the Louvres in Paris, at the Vatican and in other major western European capitals. Mitsotakis has offered to exchange the marbles for other Greek artifacts that could be shown in their place.

While the Louvres temporarily sent back some of its marbles to Greece in 2019, in exchange for other artifacts, the British museum has not relented.

Paul Cartledge, a professor emeritus of Greek culture at Cambridge University and vice-chair of the British Committee for the Return of the Parthenon Marbles, told ABC News that the responsibility lies with the British government, which would have to approve the museum's final decision by rescinding the 1816 parliamentary act that legally recognized ownership of the marbles.

"As the recent September 2021 UNESCO conference on cultural property reaffirmed," Cartledge wrote in an email, "the decision and prior negotiations have to be ultimately nation-to-nation, Greece-to-Britain, and it has to be the decision of the U.K. Parliament."