Blenheim Palace's newly installed £1million 18-carat golden toilet was stolen overnight.
The toilet - which went on display on Thursday - was stolen in the early hours of this morning and is still missing, Thames Valley Police said.
The incident happened at the palace in Woodstock, Oxfordshire, just before 5am, and "caused significant damage and flooding," police said.
Police confirmed a 66-year-old man has been arrested in connection with the incident and remains in police custody.
Visitors had to book a time slot for the fully functioning loo in advance and told to respect the three minute rule, imposed to reduce queuing times.
Detective Inspector Jess Milne, said: “The piece of art that has been stolen is a high value toilet made out of gold that was on display at the palace.
“Due to the toilet being plumbed in to the building, this has caused significant damage and flooding.
“We believe a group offenders used at least two vehicles during the offence.
“The artwork has not been recovered at this time but we are conducting a thorough investigation to find it and bring those responsible to justice.
“Residents will see an increased police presence in the area while officers and staff carry out enquiries.
“I am appealing to anyone who saw or heard anything suspicious in the area to contact police.
“You can call us on 101, quoting URN 273 (14/9), visit our website or visit a police station.”
And Blenheim Palace wrote on Twitter : "Due to an unforeseen incident at the Palace we are closed until lunchtime, the Park will remain open. Apologies for any inconvenience.
"Please note, the Palace will now be shut until 2pm. The coffee shop and gift shop will be open as normal. The 12 mile race will also still run."
They later added: "We can confirm there was an incident overnight which has led to Blenheim Palace being closed until 2pm today.
"We are working closely with Thames Valley Police and would direct any media enquiries to them at this stage.
"We hope to be able to make a fuller statement later today but do not want to do anything which could interfere with the police’s ongoing investigations."
EventSite Design, who work at the Palace, also said on Twitter: "We've had some drama overnight which I won't elaborate on just yet but it has meant we need to redirect our contractor traffic for the day."
The gold toilet was made by artist Maurizio Cattelan in 2016 to represent America's wealth and excess, and spent a year on the 5th floor of the Guggenheim, installed for museum visitors to use.
It hit the headlines in January last year when Donald Trump asked the Guggenheim Museum in New York if he could borrow a van Gogh to display at The White House.
Trump wanted van Gogh's 'Landscape with Snow, a 1888 painting showing a man
walking along a path in France with his dog.
The museum declined his request, but instead offered him the solid gold
Despite many news outlets asking Trump why he declined the gold toilet offer, the usually-loquacious President didn't provide a comment.
Asked why he was offering his work to Trump, Cattelan responded "What's the point of our life? Everything seems absurd until we die and then it makes sense."
The 'fully functioning' loo has now crossed the Atlantic and has been plumbed into the palace's pipework, yards from the room where Winston Churchill was born in 1874.
It was reportedly previously at the Guggenheim museum in New York in 2016 - and was quite a popular attraction.
The Duke of Marlborough’s half-brother and founder of the Blenheim Art Foundation Edward Spencer-Churchill told the Times: "Despite being born with a silver spoon in my mouth I have never had a s*** on a golden toilet, so I look forward to it."
He added: "It’s not going to be the easiest thing to nick.
"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."
