Currently on display at Bonhams in London is one of the greatest Roman treasures of them all, the Sevso Treasure. It's only the second time they've been on display due to their uncertain provenance:
[N]othing certain is known about the collection before 1980, when its first six pieces were reportedly sold by a Lebanese-born art dealer called Halim Korban to Peter Wilson, a former chairman of Sotheby’s. Two years later, Mr. Wilson and a London lawyer, Peter Mimpriss, persuaded Lord Northampton to invest in the venture, and four more works were acquired.
In 1983, these 10 were offered to the Getty museum, but the museum lost interest after Lebanese export licenses were proved to be falsified. That same year Mr. Wilson died, but through Mr. Mimpriss’s connections, Lord Northampton later bought four more pieces. The collection of 14, by then owned entirely by Lord Northampton, was exhibited in New York in 1990 in anticipation of a Sotheby’s auction planned for later that year in Switzerland.
The Lebanese government then obtained an injunction barring the treasure’s removal from New York, and lengthy legal proceedings followed. Lebanon dropped its claim to the collection, but Hungary and Croatia joined the case. Finally, in 1994, after several lower courts rejected the Hungarian and Croatian claims, the Appellate Division of New York’s State Supreme Court also ruled them to be “without merit,” and Lord Northampton was able to return the treasure to London.
It's a shame that such lovely things cannot be seen by the public, but are forced into hiding. At the same time, I understand the issue of stolen and smuggled antiquities is a real one. Sadly, the Sevso Treasure is caught in the middle.