‘It was magical’: hidden self-portrait by English artist Norman Cornish found at museum

The newly discovered self-portrait, which will be on display in Barnard Castle in a new exhibition of Cornish’s and LS Lowry’s work. Photograph: Claire Collinson Photography

An unseen self-portrait of one of the most popular northern English artists of his generation has been discovered hidden on the back of another painting.

The discovery of a new work by Norman Cornish – arguably the most famous artist to emerge from the north-east of England in the 20th century – was made during preparations for a big show of works by him and another titan of northern art, LS Lowry.