Carved into a wall close to a former cotton-spinning mill in the Yorkshire Dales, a simple grid would have been used by employees to take part in a game of Merrills.

But with the passing of time and the advent of more modern pastimes, both the ancient game of strategy and the "board" in the Dales have gradually faded from the public's memory.

However, it is hoped that Merrills, a more complex version of noughts and crosses which is thought to date originally from the Roman era, will now find new popularity after eagle-eyed conservators spotted the board on a wall near Gayle Mill and realised its significance.

The mill's manager, Paul Bisson, confirmed that the first mill workers are thought to have hewn the Merrills board into the wall, which was built to channel the beck through the middle of the village.

"It was probably a welcome pastime, much enjoyed as a break in their long hours at the spinning machines or carding the cotton or wool. But the game is not as easy as you might think.

"It is similar to a more complex version of noughts and crosses and a game could take a minute or half an hour, depending on how good the opponent was.

"It is fascinating to think that it has remained here throughout all these years, and anyone who did spot the board carved into the wall would not have had a clue what it was there for.

"But it is great we have realised what it is, and it gives us another little piece of social history concerning the mill."

The mill, near Hawes in Upper Wensleydale, received national publicity when it won third place in the BBC2's Restoration programme in 2004.

It closed 20 years ago, but re-opened to visitors at Easter after a £1.1m restoration was completed.

The Grade II* listed building is now run by the Gayle Mill Trust, a not-for-profit organisation which has created a wooden replica of a Merrills board. It will be on sale during a Christmas fair at the mill on Saturday, November 29.

The trust's chairman, William Lambert, discovered the rules of Merrills in a museum he was visiting in Whitehaven earlier this year and then made the connection with the board etched into the stone wall. His two daughters, Fiona, 11, and eight-year-old Rachel have now taken up the game and are proving increasingly difficult opponents, according to Mr Lambert.

He said: "It was a wonderful find during the trip to Whitehaven, and in many ways it was a quirk of fate that we managed to discover what the board had been used for.

"People had said that it was for the game of Merrills, but nobody knew how to play it. It is a game that nobody seems to know about, and it has been forgotten about during the passing of time."

The present building at Gayle was created in 1784 for Oswald and Thomas Routh as a water-powered cotton mill. However, it is thought to have been built on the site of an earlier mill – parts of which survive.

After originally being used to produce cotton, the mill later processed flax for the linen industry and then wool to supply yarn to hand knitters.

In the 19th century its role changed again when it was converted into a saw mill.

Then Gayle Beck, which flows off Dodd Fell, ceased to drive the 24ft diameter waterwheel and began powering new technology – a Williamson and Sons turbine installed in 1879.

The Williamson double vortex turbine – last used in 1948 – has been restored by Gilbert Gilkes, of Kendal, the successor to its original manufacturer.

It is reputed to be the oldest working example in the world to survive in situ and now provides the line shaft power to drive all the woodworking machinery.

The building ceased to be used as a business in 1988, although the Gayle Mill Trust took over running it earlier this year following its restoration.