A Roman coffin on display in Prince Charles's urban development in Dorset, has been destroyed by vandals.
The 1,600-year-old sarcophagus in Pummery Square, Poundbury was damaged some time late on Saturday or early on Sunday morning.
The lid of the empty sarcophagus has been removed and was damaged beyond repair, Dorset Police said.
Police community support officer Matt Barton said the stone artefact was "priceless and irreplaceable".
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"Due to the weight of the lid, it is likely to have taken several people to remove it and I am appealing for anyone who has seen anything suspicious in the area on the night in question or who has any information to contact me," he said.
Stewart Palmer, chair of the Trustees of Brownsword Hall where the coffin was on display, said the artefact, dating from about the 4th Century AD was of "very great historical interest".
He said the coffin was one of several unearthed during work on a nearby industrial estate in the 1960s. It is believed they are evidence of one the earliest Christian burial sites in Roman Britain.
When discovered, the coffin contained human remains along with remnants of cloth which indicated it held the body of a senior official.
"It's part of the history of the area - people are appalled that some lunatics decided to smash it up - it's just awful," Mr Palmer said.
In August the sarcophagus was placed on display between the columns of Brownsword Hall in the centre of Poundbury until a permanent home could be found for it.