Dr Ed Pyne snips a leaf from the Druids Oak, an 800-year-old tree that has watched over this woodland in Buckinghamshire for centuries, enduring droughts, storms, heatwaves and more.

“We know that this tree is a survivor,” he says, taking a leaf sample for DNA testing.

“Is it just that it’s got lucky? Has it led a stress-free life? Or is there something special about the genes of this tree?”

The conservation scientist from the charity, The Woodland Trust, thinks the secrets of such remarkable resilience lie in its DNA.

The experts want to understand how oaks can live for 1,000 years or more, resisting threats such as climate change and bouncing back from disease – knowledge that could be vital in restoring Britain’s depleted woodlands.

“By exploring the genome of ancient trees, we can understand how to manage them better so that we can secure their future for generations to come,” says Dr Emma Gilmartin of the tree charity, the Arboricultural Association, which is involved in the project.

English oaks are one of the UK’s best-loved trees, growing widely in parks, gardens and the countryside.

They are classed as ancient when they reach around 400 years of age.

By studying the DNA of ancient oaks, the scientists hope to unravel the genes behind the trees’ long life and their ability to survive climatic extremes.

This information would be used to select the best oak trees to plant in the future, to restore woodlands and bring back wildlife.

About 50 of the UK’s most well-known ancient oaks will be studied, including:

The Druids Oak

• Located within a nature reserve in Buckinghamshire managed by the City of London Corporation

• The tree likely dates to the 13th Century, making it older than many historical buildings

• The tree has a girth and height of about 9m

• It has been pollarded, meaning its upper branches were historically cut back to encourage regrowth above the reach of grazing animals, giving it a distinctive squat shape

• Oaks were revered by ancient druids, which may have inspired the tree’s name.

The Crouch Oak

• Found off a busy high street in Addlestone, Surrey

• One of the oldest in the borough, it is believed to be at least 800 years old

• The name “Crouch Oak” may come from the Middle English word crouche, meaning cross, possibly indicating its use as a boundary marker

• It is also referred to as Queen Elizabeth’s Picnic Tree, after Elizabeth I is said to have dined beneath it.

As well as their cultural and historical value, oaks are a haven for wildlife.

They support more life than any other native tree species in the UK, hosting more than 2,300 species, including birds, mammals, insects, fungi, and lichens.

Their leaves feed caterpillars, their bark shelters bats and beetles, and their acorns sustain mammals and birds through the winter.

Some of these species are very rare, such as the Moccas Beetle, which lives on just 14 old oak trees in Moccas Park, Herefordshire.

At the National Nature Reserve adjoining Moccas Park, conservationists are putting oaks at the heart of an effort to restore the landscape.

They are restoring a natural wildlife-rich habitat made up of open grasslands populated with ancient trees, known as wood pasture.

Acorns of ancient oaks that have stood for centuries in the area are being collected and grown into young oak trees, then put back where they once stood. Conifers that weren’t part of the natural habitat were once planted here, but these are being removed and woodlands restored.

This has led to a resurgence of rare species, including hundreds of different flies and beetles, rare bats and woodland birds.

“We’re really seeing a sort of boom in the bird population here,” says Tom Simpson of Natural England, the UK government agency responsible for protecting and improving England’s natural environment.

“In a short period of time – that’s 16 years of restoration – we are really seeing nature recovery on this site. “

As climate change and habitat loss become bigger problems, conservationists want better protection and care for ancient trees. Old trees can’t be replaced – they take decades or even centuries to grow and support many other living things.

Saul Herbert of The Woodland Trust says more needs to be done to protect these “living legends”.

“We need to find out where they are and we need to engage with people and communities to ensure that these trees are valued and looked after for the ecological, cultural and the historic value that they bring to our landscapes,” he says.