The entire herd of deer at Dyrham Park near Bath has been culled after an outbreak of bovine tuberculosis.
The National Trust, which owns and runs the site, said it had no choice but to take the extreme action after infection rates continued to rise despite efforts to control them.
National Trust General Manager Tom Boden said: “Today is an incredibly tough day and it is with a very heavy heart that we are sharing the very sad news that we have had to cull the deer herd at Dyrham.
“Unfortunately, we continued to detect very high levels of bovine tuberculosis (bTB) in the animals despite our best efforts to control the disease.
“We have been working with expert advisors and vets since the disease was first detected in 2007 but sadly infection rates reached a level that was severely impacting the health and welfare of our animals."
He said experts and staff were left with "no choice but to make the very difficult decision to humanely cull the entire deer herd", adding: “It is absolutely the last decision we wanted to have to make and we are all devastated. However, the health and welfare of the herd had to be our number one priority.”
The disease was first found among the herd in 2007, and work to try to control it has been ongoing ever since.
Additional fencing was put up to make the estate more secure, badger vaccinations were carried out and cattle was stopped from grazing on site.
Despite these efforts the disease became too widespread.
It's hoped deer will return to the estate but it's not yet known when this might be possible.
“Deer are a significant part of Dyrham’s heritage and character, having roamed the park for over 300 years," said Tom Boden.
He added: "While it is too early to say when they might return, we will aim to make Dyrham a bTB free site and bring back deer to Dyrham – back to where they belong - at some stage in the future.”
This is the first time the charity has had to cull an entire herd since 2001, when the animals were culled at Charlecote in Warwickshire. In that instance, deer were reintroduced the following year.