Some of Britain’s most ancient yews previously said to be up to 5,000 years old may be about to have millennia lopped off their estimated ages.

A new system of ageing has led to experts concluding that while the trees remain ancient and priceless, they are actually centuries younger than was previously thought.

As a result, while the Llangernyw yew in Conwy and the St Cynogs, (or Defynnog) in South Wales are revealed to be a still-venerable 1,600 and 1,200 years respectively – they are far from the 4,000-5,000 years previously claimed. The Ankerwycke yew at Runnymead in Surrey may also be more Norman then Roman, first sprouting 900 years ago rather than 2,500, but still a fair-sized tree when King John famously signed the Magna Carta at Runnymead in 1215.

The claims, published in the July issue of the Royal Forestry Society’s Quarterly Journal of Forestry, have been made by founder member of the Ancient Yew Group Toby Hindson, Dr Andy Moir from the Institute for the Environment at Brunel University and Dr Peter Thomas, a plant ecologist at Keele and Harvard Universities and vindicate previous work done by researchers such as Robert Bevan-Jones.

Their research is based on extensive studies of ancient yews in Sussex, and is inspired by “Unified Field Theory”, uniting different methods based on tree-girth, tree-rings and historic rates of growth which had previously generated their own incomplete and competing pictures. United they give a more complete picture even allowing the new theory to take into account the irregularities of growth common in yews, especially very old ones.

Toby Hindson says errors may have crept in before because the trouble with yew ageing is the bigger the yew, the more theoretical its age “A method which is able to take into account everything we know about old yews and how they grow is likeliest to give an accurate age answer, and the new ageing method is the result of such a system.”

“But despite these findings, people should still allow themselves to be amazed at the ancient living world around us. While 1,600 years, or in the case of one individual, 2,000 years, for the UK’s oldest living yews may seem low in terms of the inflated ages which many people have grown used to, it really still is extremely old.

“To place in context, these oldest specimens would have been standing when Britain was ruled by the Saxons and the very oldest may have been young at the time of the Roman invasion – just not in the Bronze Age.

“Imagine trying to replace a yew that has stood for even 500 years. The grower would have had to begin work about the reign of Henry VIII. A tree of this kind of age remains priceless and irreplaceable in terms of its age.”

Mr Hindson explains that a woodland is designated “ancient” if it is more than 400 years old, and says one problem with the inflated age claims of up to 5,000 years is that they diminish the perceived value of trees which have stood for half a millennium and are witness to a huge span of history.

“The ageing of specimens up to 5 or 6 metres in girth remains unchanged by the new method, as does the importance of preserving our old yews because of their vast antiquity.”