Sketch for altarpiece was so badly creased and crinkled it could not be put on exhibition for centuries
A 16th-century drawing that has not been on display for more than 400 years because of its poor condition will finally be exhibited after a painstaking conservation project.
The work by Bernardino Campi, a late Renaissance Italian artist, is a sketch for an altarpiece painting of the Virgin and Child.
It has been part of the Royal Collection for 200 years, but it was unable to be displayed because its surface was so creased and crinkled.
Now the major project taking 120 hours has stabilised its fragile condition, allowing it to be shown in the King's Gallery at Buckingham Palace.
It will be exhibited alongside works including masterpieces by Leonardo and Michelangelo, in a major exhibition that opens on Friday, Nov 1.
The artwork is known as a cartoon, from the Italian word "cartone" - a large sheet of paper.
They rarely survive as they were functional tools of the trade that were never intended as works of art in their own right.
Artists used poor-quality paper that often would be damaged during the transfer process, either by pricking or incising the outlines, or with a grid to enlarge the design square by square, as in this example.
Research has revealed the drawing was created for an altarpiece in a church in the town of Codogno, south-east of Milan. Campi was in particular demand for altarpieces and frescoes in churches.