A recently discovered painting by the surrealist artist Leonora Carrington, made during her confinement in a Spanish psychiatric hospital during the second world war, will go on public display for the first time in London this summer.Known as Villa Pilar, the work was painted in 1940 while Carrington was a patient at sanatorium Morales in Santander, after fleeing Nazi-occupied France after the arrest of her partner, the German artist Max Ernst.Carrington suffered a psychological breakdown in Madrid and was admitted to the institution, where she underwent traumatic psychiatric treatments that she later described in her memoir Down Below.But encouraged by her psychiatrist, Dr Luis Morales, Carrington sketched each day, and created two paintings, Down Below and Villa Pilar, which depict the psychiatric hospital as a symbolic underworld. Carrington described her “down below” period as an experience akin to “being dead”.Villa Pilar will join the exhibition Leonora Carrington – the Symptomatic Surreal at the Freud museum, where Sigmund Freud spent the final year of his life after escaping Nazi-occupied Vienna. To mark the unveiling, the exhibition has been extended until 10 August before travelling to Faro Santander, a new arts centre in the northern Spanish city, in September.Carrington, who was born into a wealthy Lancashire family in 1917, rebelled early against the expectations placed on upper-class women. She studied at the Chelsea School of Art before meeting Ernst at a dinner party in London in 1937, when she was 20 and he was 46. The two began a relationship that scandalised their respective social circles and moved together to Saint-Martin-d’Ardèche in the south of France, where they lived and worked until the German invasion.