The carcass of a swan owned by the Queen has been found near to Windsor Castle after apparently being barbecued and left to rot.
It is believed the bird was butchered and stripped of its flesh at some point over the weekend.
The grisly remains were discovered at Baths Island in Berkshire on Sunday afternoon.
Wendy Hermon, 46, of the charity Swan Lifeline which cares for sick and injured birds, said she discovered the "sickening" scene on Sunday afternoon.
"It was just a carcass, it was all burnt. We could see that whoever did this had taken the breast out," she said.
"It was done neatly, presumably to get at the meat. They had skinned it as well and possibly barbecued it there, on a disposable barbecue.
"We have no idea how it was killed, it could have been shot or beaten.
"I felt sick when I saw it. How can someone do that and leave it where they did? I would have been devastated if I had been walking along there with my little boy and he had seen that.
"It just sickens me that there are people out there that do things like that."
All wild mute swans in the the UK are the property of the Crown and it is a criminal offence to kill one. Killing or injuring a swan was once classed as treason under a law dating back to the 12th century. The birds are now protected under the Wildlife and Countryside Act 1981.
Thames Valley Police spokesman said: "Thames Valley Police is investigating a theft following a report at 12.38pm on August 18 by a Royal Borough of Windsor and Maidenhead Council warden who had found a swan. The swan had been killed and burnt."
Centuries ago, their meat was considered a delicacy and was served at banquets.