The work of a lesser-known German artist (right) was altered to look like a Holbein (left)

The National Gallery is dusting off some of its most embarrassing acquisitions for a new exhibition looking at fake artworks.

Close Examination will display works of art that have been quietly removed from view after research showed they were not what they were thought to be. They include works supposedly by Sandro Botticelli and Hans Holbein which were mistakenly thought to be genuine.

The exhibition is billed as a celebration of "the remarkable collaboration of scientists, conservators and art historians" at the central London gallery. More than 40 works of art will go on display at the gallery in June.

Pastiche

Spread across six rooms, the works represent some of the biggest challenges faced by gallery experts.

In June 1874, the gallery paid more for a fake than a real Botticelli when two pieces were purchased at the same time.

Venus and Mars was bought along with the more expensive An Allegory, which was thought to be a companion piece. Only later was the latter discovered to be a pastiche painted by a follower in the style of Botticelli. The paintings will be displayed alongside one another at the exhibition.

Also on show will be a portrait acquired by the National Gallery in 1990 which was believed to be by Holbein. But microscopic paint analysis revealed Portrait of Alexander Mornauer (about 1464-88) was altered to resemble a work by the German master.

Conservators were able to safely remove these additions to return the painting to its original state. One room in the exhibition looks at work by great artists that were rediscovered through a combination of scientific analysis, conservation, and art historical research.

Raphael's original painting of The Madonna of the Pinks, whose whereabouts was unknown until 1991, will also be on display.

During a visit to Alnwick Castle in Northumberland, Dr Nicholas Penny - now director of the National Gallery - spotted the painting and decided it warranted closer examination.

Infrared reflectograms confirmed the work as a genuine Raphael.

Close Examination: Fakes, Mistakes and Discoveries opens on 30 June and runs until 12 September.