A solid gold toilet which was stolen from Blenheim Palace in an overnight raid has been valued at £4.8m, the palace CEO has revealed.
The 18-carat lavatory, which was initially reported to be worth £1m, was taken by a gang during an break-in at around 4.50am on Saturday, Thames Valley Police said.
The fully functioning loo, made by Italian artist Maurizio Cattelan, titled "America", has not yet been found but a 66-year-old man has been arrested.
The theft of the sculpture from a wood-panelled room at the 18th-century Oxfordshire estate caused significant flood damage as it had been plumbed in for visitors to use.
Reports had said it was worth an estimated £1 million but Blenheim Palace chief executive Dominic Hare said the artwork is valued at about six million US dollars (£4.8 million).
He said: "We have a very sophisticated security operation and we have not had an incident like this in living memory.
"The events of the last 24 hours mean we may have reason to reconsider some of our systems.
"There is always a risk when you display valuable art to the public, but it is worth that risk, even now, it was still worth that risk."
Mr Hare said he believed Mr Cattelan attended a reception party marking the exhibition launch on Friday night, adding: "I understand he is very shaken and shocked."
The sculpture hit the headlines last year after it was offered to US president Donald Trump by the chief curator of the Guggenheim museum in New York, its former home.
It was installed at the country home of the aristocratic Marlborough family as part of Mr Cattelan's exhibition, which began on Thursday.
The toilet had been installed opposite the room where Winston Churchill was born, and was free for use by visitors to the 18th Century heritage site.
Art, or lav, lovers simply needed to book their time-slot in the cubicle in advance, with 20 slots an hour to choose from.
It proved so popular that people queued for hours to place their cheeks upon its solid-gold seat, with some 100,000 using it for its intended purpose.
The golden toilet had proved popular at the Guggenheim and has been described by critics as a pointed satire against the excesses of wealth.
The piece made headlines in 2017 when it was offered on loan to Donald Trump.
The US president had initially asked the museum to lend him an 1888 Van Gogh painting, but it rejected the request, offering Cattelan's "America" instead.
The theft comes after the Duke of Marlborough's half-brother, Edward Spencer-Churchill, said last month the artwork would not be "the easiest thing to nick".
Mr Hare urged anyone with any information to contact police.
He said: "We are saddened by this extraordinary event, but also relieved no-one was hurt.
"It's a great shame an item so precious has been taken, but we still have so many fascinating treasures in the palace and the remaining items of the exhibition to share.
"The investigation continues, but it will be business as usual from tomorrow, so visitors can continue to come and experience all we have to offer."
Mr Spencer-Churchill told the Times: "Firstly, it's plumbed in, and secondly, a potential thief will have no idea who last used the toilet or what they ate.
"So no, I don't plan to be guarding it."
Inspector Richard Nicholls from Thames Valley Police said: "A group of offenders broke into the palace and stole a high value toilet made out of gold that was on display.
"We believe they used at least two vehicles during the offence and left the scene at around 4.50am.
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"The artwork has not been recovered at this time, but there is a thorough investigation being carried out."
Inspector Nicholls said Friday's reception party "would form part of our inquiries in order to ascertain events leading up to the item being stolen".
He added that commenting on how the property was accessed "would be speculation at the moment".
Hours after the Blenheim Palace burglary was announced, Thames Valley Police said detectives were scouring CCTV in their bid to uncover the culprits.