A rare 16th Century astronomy book written by a Welshman has sold for £10,000 at auction.
A first edition of The Castle of Knowledge by Robert Recorde - the man who also invented the equals sign (=) - was published in 1556.
That was eight years before the birth of the Italian Galileo, regarded as the father of observational astronomy.
It was found in a box of antiquarian books by Hansons Auctioneers, whose Jim Spencer called it an "amazing" find.
He said: "It might be the most important scientific text I've ever handled. It's the first astronomical treatise to be published in English.
"In terms of copies coming up for sale - it's almost unheard of."
Recorde was born in Tenby, Pembrokeshire, in 1510, and left at just 15 to study maths at Oxford.
In 1545, he went to Cambridge to study medicine, and became physician to the young King Edward VI and, after his death from TB, to Queen Mary.
'It felt special'
Mr Spencer said a client brought in a box with probably about 40 books with a range of dates.
"This one jumped out at me, with its allegorical woodcut title page and charming illustrations. It felt special."
He added that while the book was well preserved, some leaves had been lost over time.
"Usually to a book collector that would wipe out all collectible value, but because it's so scarce and important, I thought collectors should look beyond the flaws, and appreciate the fact they're not going to buy it anywhere else.
"It's possible they might not see another copy for sale in their lifetime."
Mr Spencer said research quickly revealed its significance and scarcity.
"Robert Recorde seemed to be a bit of an unsung academic, so I feel he wasn't or isn't as well known as he deserves to be.
"Everyone has heard of Galileo and Isaac Newton, but why not Robert Recorde?
"He invented the equals sign, and he introduced the pre-existing plus (+) and minus (-) signs to English speakers in 1557.
"Yet many people have not heard of him, partly because of his tragic end - he died in jail."
Mr Spencer said he could only find one other copy that sold at auction and that went for £74,200 in 2007.