There is a good piece in tomorrow's Guardian about the authenticity of the Warren Cup in the British Museum:
On Wednesday, 15 years after the British Museum bought the Warren cup for £1.8m, it was denounced by a highly respected German archaeologist as a forgery.
At a public debate staged by King's College London, Prof Luca Giuliani challenged the museum's view that it dates from the 1st century AD and the reign of the emperor Nero.
The professor of classical archaeology at Humboldt University in Berlin dismissed it as a creation of the early 20th century, arguing that such explicit imagery is unprecedented in Roman silverware. He suggested instead that the cup was designed for the pleasure of its former owner – a wealthy American gay man, Edward Perry Warren, who bought it in Rome in 1911, and who also acquired other "counterfeit" pieces, he said.
A conversation with the irritatingly brilliant Armand D'Angour a couple of weeks ago put me on the right path, though I uncharitably damned him at the time for spoiling my illusions.
It has long been regarded as a fake/forgery.
Anyone else who still thinks it might be Roman should rush to a library and get hold of MT Marabini Moevs' "Per una storia del gusto: riconsiderazioni sul Calice Warren," Italy Ministero Per I Beni Culturali E Ambientali Bollettino Darte 146 (2008), pp. 1-16. An extract can be read here. More background on Edward Perry Warren in this 2012 doctoral thesis here.
UPDATE The story is also covered in the Daily Mail this morning