The painter known as Gluck was born Hannah Gluckstein in 1895, into the family who owned the Lyons catering empire. She defied their ideas of a woman’s place. Stylish photographs of her in the 1920s by Hoppé and in the ’3os by Angus McBean show her in men’s clothes with barbered hair. She exhibited her work in a signature tiered frame, only in “one-man shows”, and on the backs of publicity photographs wrote “please return in good condition to Gluck, no prefix, suffix or quotes.”

Gluck referred to Medallion (1936), her double portrait of herself and her lover Nesta Obermer, as the “YouWe” picture and their marriage picture. On 23 June 1936 they’d been to Fritz Busch’s production of Mozart’s Don Giovanni at Glyndebourne. They sat in the third row of the stalls and Gluck felt the intensity of the music fused them into one. The “YouWe” painting followed. It was her public declaration of love and commitment. “Now it is out,” she wrote to Nesta, “and to the rest of the Universe I call Beware! Beware! We are not to be trifled with.”

Medallion has the feel of propaganda art. Gluck appears in the foreground. She was 41 in 1936 and, until this coup de foudre, had been in a four-year relationship with Constance Spry, florist par excellence to royalty and high society. Nesta was 43 with a glittering social life and a wealthy elderly husband whom she had no wish to offend. In Medallion they stare determinedly into their merged future. Nesta’s eye seems lit by paradisal light.

The painting was included in Gluck’s highly praised 1937 exhibition at The Fine Art Society. It hung alongside her portraits of society figures and her exquisite paintings of Spry’s flower arrangements. The Queen visited the gallery on 25 November and according to the Court and Society column of the Daily Mail, “Her Majesty, who was wearing a swagger suit of peacock blue velvet with a hat of the same colour, spent a considerable time discussing the pictures with the artist".

Quite what the Queen made of “YouWe” is not on record. Nine years earlier Radclyffe Hall’s novel The Well of Loneliness had been censored as obscene and destroyed, solely because of its lesbian theme. “I would rather give a healthy boy or a healthy girl a phial of prussic acid than this book,” wrote the Editor of the Sunday Express by way of review.