Back in the early 1500s Thomas Ap Harri was riding home from a hunting expedition with some friends on Halkyn Mountain when they struck a wager that he and his horse couldn't jump one of the mineshafts that dot the area.

The bold Thomas, possibly fortified by drink, was up for the challenge and he and his faithful steed soared clear – the feat commemorated by two standing stones 25 feet apart marking where the horse took off and landed.

It also gave rise to the name of the nearby village, Naid y March (Horse's Leap) on Halkyn Mountain, in Flintshire, which has been mined for lead since Roman times.

Now thanks to rural development agency Cadwyn Clwyd, the spot where Thomas and his horse passed into legend is to be marked with a special display with a panel depicting the historic jump. The picture that Flintshire Countryside Service has commissioned is by Bethesda artist Chris Hull (who has done other work on the mountain) and will be placed inside an iron frame made by local blacksmith Richard Jones.

This will be decorated with intricate metalwork showing horses, other animals from the mountain including sheep and great crested newts and flora such as the rare spring sandwort – or leadwort – which thrives on the heaps of toxic lead spoil.

There will also be iron railings enclosing the mineshaft and the two stones.

The cost of the work is being met by Groundwork Flintshire and Wrexham using funds provided by the CEMEX Foundation, a charitable trust set up by quarrying company CEMEX who are assisting with five Groundwork projects in the UK.

Halkyn Mountain ranger Rachael Watson said: "It's a fascinating story and one very much in keeping with Halkyn Mountain Common.

"Thomas Ap Harri really did exist and was an ancestor of the Piers Mostyn family of Talacre.

"In 1540 his son Harri Ap Harri bought Basingwerk Abbey, near Holywell, when Henry VIII was dissolving the monasteries.

"The standing stones are actually Bronze Age in origin and must have come from somewhere else but were brought to the spot to mark Thomas's achievement.

"His horse wouldn't have been a modern hunter either but a much heavier and sturdier animal, not really suited to jumping, so it would have been a pretty brave – or foolhardy – thing to do.

"But the common is still hugely popular with horseriders and many of them have moved to the area because it offers such good opportunities to ride amid such stunning scenery."

Rachael is the first person to be appointed ranger for the 1800-acre sweep of Halkyn Mountain Common, a stunning landscape of humps and hollows 800 feet above sea level carved out by centuries of lead mining, quarrying and grazing.

The common is not only a Site of Special Scientific Interest but also a Special Conservation Area and it is also part of the Green Mines Project which links five former mining areas in Western Europe.

Cadwyn Clwyd project support officer Mari Williams is in charge of the Halkyn Mountain Project and she says: "The other project sites are in Ireland, Portugal, Spain and at Blaenau Gwent.

"The aim is to look at ways these former mining areas are trying to reclaim the landscape while preserving the industrial heritage of these sites.

"The idea is that we can interact with the other countries and see how they cope with the problems associated with mining and learn from each other.

"We visited the Portuguese site in Alentejo where there is a former copper mine and a delegation will come to Wales in January."

Another current project on Halkyn Mountain is the installation of cattle grids on the roads onto the common which helps safeguard the ancient rights of the graziers to allow their flocks of sheep to wander the area.

"The graziers play a very important part in the preservation of the mountain," explained Mari: "The sheep graze the common and so maintain that unique landscape."

While the lead mining may have stopped in 1987, grazing continues as does quarrying, with the mountain remaining one of the most intensively quarried areas in Wales.