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.
