Portrait of Gainsborough's nephew will sparkle in National Portrait Gallery show thanks to conservators
The painting, which took the artist less than an hour to paint, was restored for the National Portrait Gallery's exhibition opening in London this week
Restoration of rare English Medieval altarpiece reveals a history of serial vandalism
The Battel Hall retable, which survived the fury of 16th-century iconoclasts, bears later scars of graffiti and "witchmarks" against evil spirits