Written by Jack Guy, CNN

Authenticity is a constant concern in the art world, whether it's a French museum discovering half its paintings are fake or police fooling thieves into stealing a replica 17th-century masterpiece in Italy.

But now a team of art conservators have had a rather more pleasant surprise.

What was thought to be an imitation of Sandro Botticelli's 15th-century masterpiece "Madonna of the Pomegranate" in fact comes from the artist's own workshop, according to conservation charity English Heritage.

Cleaning revealed the painting's true colors from underneath a thick layer of varnish, said the charity in a statement, showing the work to be an authentic Botticelli.

Rachel Turnbull of English Heritage works on the painting. Credit: Christopher Ison/English Heritage

"Madonna of the Pomegranate (Madonna della Melagrana)" was supposedly painted around 1487 by the Italian master. It shows the Madonna and the Christ Child holding a pomegranate -- which symbolizes Christ's future suffering -- with four angels around them.

The original is on display in the Uffizi Gallery in Florence, and experts had believed that the painting held by English Heritage was an imitation due to variations in certain details and the yellow varnish that covered it.

Layers of dirt, overpaint and varnish were removed as part of the restoration process. Credit: Christopher Ison/English Heritage

However, pigment analysis, X-ray testing and infrared studies have led English Heritage to believe the painting was produced in Botticelli's workshop in Florence. It was customary for workshops during the Renaissance to produce several versions of a popular painting, with varying degrees of input from a master artist.

"Being able to closely examine and conserve this painting for the first time in over 100 years has really given us the chance to get up close and personal with the paintwork," said Rachel Turnbull, English Heritage's Senior Collections Conservator, in a statement.

"I noticed instantly that the painting bore a striking resemblance to the workshop of Botticelli himself; stylistically it was too similar to be an imitation, it was of the right period, it was technically correct and it was painted on poplar, a material commonly used at the time."

The provenance of the painting was confirmed after consultation with experts at the Victoria and Albert Museum and the National Gallery in London, according to the statement.

While the painting might originate from Botticelli's workshop, that is not to say it was painted entirely by the master himself. Botticelli employed various assistants to help him keep up with demand for his work, and they would paint smaller versions of popular works for customers on a smaller budget.

It will go on display to the public at Ranger's House in Greenwich, London, on April 1, as part of the Wernher Collection, which consists of about 700 works bought by diamond magnate Julius Wernher in the 19th century.