This example demonstrates the value of expert knowledge in identifying a well-documented portrait obscured by varnish and over painting.

 

“The portrait of Milton as an undergraduate (NPG, 4222), which is recorded in the collection of Milton’s widow, disappeared in the early nineteenth-century when it was sold from the collection of Speaker Onslow. It re-appeared in a minor sale-room in London in 1961, obscured by layers of varnish and over-paint, and was recognized as the missing portrait by the Gallery staff, but, luckily, no-one else; it was purchased for £22.”

 

RL Ormond, ‘The National Portrait Gallery archive’, Journal of the Society of Archivists, 4 (1970), 130-136.