The auction house was furious that the Italian authorities gave just 24 hours' notice about the objects' suspect provenance.
"We were a bit miffed to say the least," a spokesman said. "You can imagine the amount of work that goes into marketing a sale like this around the world.
"Obviously we are not in the business of selling something that shouldn't be sold, but to have a demand made like this at such short notice is not something we take lightly."
Many of the pieces had due to be sold as part of the (Australian) Graham Geddes collection. The Telegraph added:
Bonhams said it expected Italy to make a formal claim on the antiquities, which were owned by British, Australian and American collectors.
Meanwhile Theo Toebosch writing for the NRC Handelsblad has picked up on the reason why Bonhams should have been suspicious and should have conducted a more rigorous "due diligence" process: the revelations made about antiquities from Italy surfacing through Sotheby's in London during the 1980s and early 1990s (see Peter Watson, Sotheby's: Inside Story [London 1997] [WorldCat] [American edition]). At least seven of the withdrawn pieces were derived from this route. Toebosch also comments on the unrepentant tone of the Bonhams press release.