An antique dealer who bought a stained glass window in a charity shop for £20 says it belonged to Robert the Bruce - and could be priceless.

Richard Drummond, 49, spotted

the colourful glass for sale in Moffat in Scotland.

He was told it had been discovered in an old house in the area and abandoned for years.

Robert paid just £20 for it and began cleaning years of grease to reveal the stunning stained glass underneath.

It showed a depiction of what could be a knight

- with a Latin inscription around the edges which Richard roughly translates into 'Robert Bruce, King of the Scots."

Richard began carrying out his own research delving online for information and seeking out the help of local and international experts to determine the age of the relic.

He now believes it dates back to the 14th century and may have be installed in a castle taken over by the famous king.

Richard believes it is a ''massive historical find'' for the country and he's hoping for it to be in a museum in Scotland - if it is proven historically important.

Richard's son, Alfie, and the glass appear on an upcoming episode of the BBC's The Bidding Room - where experts confirmed it could be up to 700 years old.

Richard said: "It could be priceless. If this is proven to be of that period"

it's a massive historical find for Scotland.

''I cleaned it up, using a bit of bicarbonate soda and vinegar just to get the grease off the top.

''Once I revealed some of the artwork from underneath, I stopped using that.

"I used a bit of water and cleaned it off with a brush, then I could see it said 'Robert Rex Scotorum' - that's when I thought this was going to be interesting."

"I started having a closer look at the glass itself, seeing the engravings and the way it was painted."

"I'm not an expert but I've got enough knowledge to know when something looks really old."

"I got the local museum curator round the same day for a quick look - he said he it was hundreds of years old in his opinion."

Richard believes the glass may have come from France via the Knights Templar, while one expert he consulted believes it once sat in a window in a castle taken over by the conquering king.

Richard said: "One expert believes it was in a turret at some point, and when it's got the name of a king on it, chances are it's got to belong to some kind of castle. "

"Which castle that is, I have no idea."

Richard is now on a mission to get the artefact dated and find out exactly where it came from.

He said: "Is this part of the treasure that left France in 1307?"

Is this something that was made in Scotland and England for Robert the Bruce?

"Was it made in memory of him? It's medieval art,"

it's medieval Scottish history, and in my eyes, it's just stunning.

"It's huge, and so well preserved - it's been looked after."

It's just been a piece of history that's been forgotten about in Moffat.

"My hope is that we can get it tested, and that it does come back that it is medieval and hopefully we can give it a date."