An ancient oak tree that has stood in the heart of a famous forest for hundreds of years and is linked to the legend of Robin Hood has died, experts believe.

The Major Oak is estimated to have lived in Sherwood Forest in Nottinghamshire for up to 1,200 years, and is considered one of Britain's biggest oak trees.

Conservationists worked to protect the tree, which attracted millions of visitors over its life, but in recent years the natural giant was in decline.

The Royal Society for the Protection of Birds (RSPB) - the conservation charity which manages the forest - said after the tree's first spring with no leaves this year, scientific experts believed the Major Oak had died.

While it was difficult to determine the exact cause of the oak's demise, the RSPB said a combination of issues - including years of "well-intentioned structural intervention and huge amounts of human activity" around the tree - were thought to be "major contributors".

The charity said the effects of climate change - including recent heatwaves and droughts - had compounded challenges it would naturally be facing at its age.

The Major Oak will remain in place at Sherwood Forest as a habitat for wildlife and "natural monument" for visitors. Saplings from the tree have also been planted across the world.

Legend has it that the outlaw Robin Hood used the Major Oak's hollow trunk - which in fact was caused by fungi - as his hideout.

The oak had many names but the "Major" stuck after the tree was mentioned in a book in 1790 by Major Hayman Rooke - a former British Army soldier who lived in Mansfield Woodhouse - a few miles from Sherwood Forest - after he left the military.

According to the RSPB, the book prompted the first waves of tourism to the forest and the "world-famous" tree.

Legendary actor Dame Judi Dench is known for her love of ancient oak trees, and has paid tribute to the Major Oak.

Dame Dench, patron and ambassador for the Woodland Trust, said: "The Major Oak has provided inspiration for countless stories, poems, paintings and people for more than 1,000 years - all the while itself teeming with life and providing a home to an enormous range of wildlife.

"I was lucky enough to plant an oak sapling from Sherwood Forest with Woodland Trust CEO Darren Moorcroft in my garden recently. It has a special place alongside the cutting from the Sycamore Gap tree.

"I hope everyone who has been inspired by the Major Oak or another ancient tree reaches out to their MP and asks them to improve legal protections for these iconic and vital elements of our national landscape."

While the stories surrounding the ancient tree and its home have drawn visitors to the site, its distinctive long limbs, sprawling canopy and hollowing trunk - with a circumference of about 11 metres - have also made it an iconic landmark in Nottinghamshire.

At one time, visitors would climb into the oak's hollow trunk but from the 1970s, when a fence was placed around the tree, it was appreciated from a distance.

Early efforts to preserve and protect the tree included supports for some of its larger branches and while intended to help the oak, they were likely to have contributed to its demise, the RSPB added.

Over the last few years, it was noted that the Major Oak had a "noticeable reduction" in the quality and quantity of its leaves.

Recent conservation work had focused on the soil under the tree, which had become compacted from the footfall of its many visitors, the RSPB said.

The charity added compaction made it harder for rainwater to penetrate the soil and for the tree's root system to take in the oxygen and nutrients it needed.

Ed Pyne, Woodland Trust senior conservation adviser, said it was "one of the country's most important trees".

"To see the loss of a tree like this is always incredibly tragic," he told the BBC. "The Major Oak is perhaps the most famous ancient tree in the UK.

"We've learned so much from the work that we've done... that we could go and apply to other trees across the country."

He added - had it not been for challenges like climate change and 200 years of visiting tourists compacting the soil around it - the tree could have lived for hundreds more years, as trees "do not die of old age".

Chloe Ryder, RSPB Sherwood Forest estates operations manager, said the cause of the tree's death was "complicated", but agreed that tourism had played a part by compacting the soil.

She said staff had done "everything they can" since taking over the site to keep it alive.

"It is of such importance to Sherwood Forest," she added.

"We now know that it's come too late, right at the end stages of its life.

"But there wasn't anything more that we could be done unless you invent a time machine, really."

Pyne added the tree would not immediately disappear, and as it decayed over the next few decades, would provide a home to many animals and plants.

Simon Parfey, a specialist in soil microbiology testing - who had been part of an expert team caring for the tree since 2021 - said the soil around the tree was "under far greater stress than anyone had initially realised".

"While the Major Oak team worked tirelessly to revive the environment around this iconic tree - and saw encouraging signs of life in some areas - the damage, it now seems, was already too deeply entrenched to fully reverse," he said.

Parfey said the lessons learned from the Major Oak would help to care for other ancient trees across Britain.

"The Major Oak's true legacy is no longer just in folklore, but in the future of conservation," he said.

The RSPB dispelled rumours the oak tree would die in the winter of 2024, but said it had endured challenges.

Throughout its long life, the tree had survived fires, winds and snowstorms and more recently, the extreme weather that comes with climate change.

Reg Harris, the director of a tree surveying firm who said he had been monitoring the tree's health for the RSPB for the past nine years, added: "The most recent decline has corresponded with five very hot and droughty summers, most notably in July 2022 when the UK experienced record temperatures of 40 degrees Celsius."

However, he said it was "impossible to pinpoint a single cause" for the tree's decline.