An ancient oak tree reputedly used as a hideout by Robin Hood has been damaged.
A three-foot-long section of bark was broken off the tree in Sherwood Forest, Nottinghamshire, by people climbing it, the charity that manages the site said.
The Major Oak is about 1,000 years old and has been fenced off since the 1970s to protect it.
The RSPB said the damage was "heartbreaking... especially at a time when nature had been providing solace during lockdown".
Fibreglass used to protect the tree's hollow trunk was also damaged, the charity said.
Gemma Howarth, site manager at Sherwood, said: "The Major Oak is a massively important part of our national heritage both in terms of our natural world and the Robin Hood legend which brings so many people to Sherwood from around the world.
"The vast majority of people who visit the area want to come and see the Major Oak."
The tree is hollow inside and has a hole in the trunk which visitors used to climb inside.
However, the area around the tree's roots was fenced off in the 1970s when conservationists recognised the damage being caused.
Ms Howarth spotted the break in the tree's bark, which was about three-foot long and a foot wide, during a check of the site.
She believes the tree was damaged "during the lockdown period when the forest was quieter, probably by someone stepping on it to get inside".
"But no-one should have been near it in the first place," she said.
"This fantastic tree isn't something we can just re-grow - it has survived a thousand years of history.
"We want it to be here for many more years to come."