Thought to be as old as Bonnie Prince Charlie, a sweet chestnut at Murthly Castle in Perthshire is the 15,000th Scottish tree specimen to be mapped by amateur tree hunters.

The ancient sweet chestnut at Murthly became the 15,000th Scottish tree to be recorded in the Ancient Tree Inventory.

Estimated to be over 300 years old, it has a remarkable trunk girth of 5.5m.

Welcoming the tree hunters to Castle Murthly Estate, Thomas Steuart Fothringham said: “We are delighted our sweet chestnut is the 15,000th tree to go on the inventory. The designed landscape has been a feature at Murthly for half a millennium and continues to be highly valued.”

Untrained enthusiasts working with the Woodland Trust are mapping the oldest and most important specimens across the country so they can be protected.

The Murthly Castle tree’s vital statistics were taken down by Judy Dowling from St Andrews, Joan Sneddon from Largo, Noel Fojut from Berwickshire, Clair McFarlan from Dumfries and Lorna Holl from Balmaha. The Ancient Tree Inventory began as the Heritage Lottery funded Ancient Tree Hunt in January 2006.

The UK’s ancient trees have no automatic right of protection. There is no equivalent to Scheduled Ancient Monument status which important archaeological sites have.

The famous Fortingall Yew – judged to be at least 2000 years old – highlights the disparity. The wall around the tree attracts formal legal protection rather than the tree itself.

Kylie Harrison Mellor, Woodland Trust’s citizen science officer said: “Ancient trees are as much a part of our heritage as stately homes, cathedrals and works of art, but they don’t get the same protection. Identifying where ancient trees are takes us one step closer to giving them the care and protection they need.

“So today’s recording of the 15,000th tree in Scotland is really worth celebrating – and so are the efforts of the dedicated band of tree recorders and verifiers who do this important work.”

A map of all the recorded trees can be viewed at ati.woodlandtrust.org.uk where there is also further information on the inventory including details of becoming involved.