Helene, who is now 88 and lives in Florida, said the painting stood out when she first spotted it.
“My background in art history and studio practice drew me to this piece instantly,” she said.
“The painting had an undeniable, regal presence, but it was the colour theory at play that held my attention.
“The way the pastels were integrated into the composition was both interesting and bold – it was clearly the work of a significant hand with a deep understanding of light and form.”
Barry said the family were amazed to find out who the artist was having grown up with picture on the wall.
He said: “We were, as you can imagine, delighted and astounded when we found out the identity of the artist and of the model.
“For mum, it was confirmation of her artistic eye and ability to recognise great talent.”