Louise Yeoman: Historian attacks Rosslyn Chapel for 'cashing in on Da Vinci Code'
The author and academic said the medieval chapel in Midlothian was built by William Sinclair so that Mass could be said for the souls of his family.
She condemned those who believed it was at the centre of a conspiracy and said the chapel, looked after by the Rosslyn Chapel Trust, perpetuated a false image to cash in on the popularity of The Da Vinci Code.
Dr Yeoman said: "William Sinclair built this beautiful church for the saying and the hearing of Mass.
"He built it for his soul and the souls of his family, yet it has been taken over by a rabble of conspiracy theories, many of them anti-Catholic and absolutely ludicrous.
"The level of misunderstanding and ignorance you need to think this is some sort of pagan, occult conspiracy is huge.
"It is like a biologist being faced by people who think you could actually get all the animals on Noah's Ark.
"There needs to be some sort of proper interpretation telling people that this is a medieval Catholic church, and telling people more about Scottish medieval piety.
"If people want to stuff the bookshop full of that rubbish, then fine, but it should not seep into the official guides or interpretation."
Dr Yeoman said tourist guides and information boards within the chapel, seven miles south of Edinburgh, falsified its history.
She said: "I was in Rosslyn Chapel recently and the first thing I heard was a guide telling people nonsense about Robert the Bruce and the Knights Templar. I wanted to tell people, 'Sorry, I hope you have not paid money for this; that's awful'.
"What really upsets me is that they know the Knights Templar connection is false, yet they still perpetuate the myth on their interpretation boards."
Dr Yeoman said Historic Scotland had done a lot to safeguard the chapel by scheduling the site and land around it.
She called for the chapel to be preserved in its intended manner, as a place of piety.
Stewart Beattie, the project director for the Rosslyn Chapel Trust, said it was sometimes difficult to persuade tourists that the building was not exactly as Dan Brown depicted it.
He said: "Dan Brown has caused us a few problems, because the book mentions specifics which are not here.
"People come along and say we have put a carpet down to disguise a star of David on the floor, because the book says it is there and so it must be.
"On occasion we have actually had to lift the carpet to show it is not there."