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How was Rembrandt painting verified?

11 June 2014 Last updated at 00:12 BST

A painting given to a National Trust property in Devon has been verified as a genuine Rembrandt.

The authenticity of the self-portrait which hangs in Buckland Abbey has been under debate for decades. But now eight months of investigative work has confirmed it was painted by the Dutch artist and is estimated to be worth £30m.

National Trust Paintings Conservation Adviser Christine Sitwell explains to Anna Varle why the authenticity was in doubt - and how it was verified.