A picture of her hometown hangs in the museum, her only known work of Tenby, believed to have been painted while she was a student in London.
Judith Mackrell, writer and John’s biographer, said: “She’s painted the beach at twilight so there’s already a ghosting of melancholy about it, and there are these two family groups and it’s significant that there are no fathers in either group, as if reflecting the utter emotional absence of her own father.
“The two young mothers in the groups, there’s something very idealised about them, the very sweet attentiveness that they are paying to their children, as if Gwen was drawing on her own last happy memories of her mother.”
Longtime John fan, Nicky Wire of the Manic Street Preachers, said this was the first painting of hers he ever saw.
“It’s something of an outlier because it’s very much the exterior world and her art didn’t really end up like this.”
The bassist wrote a song inspired by the complex relationship between John and her younger brother Augustus, The Secret He Had Missed.
Each had a very different outlook on art and its role in life.
Wire said while Augustus “wants to make the world his”, his sister wanted to “retreat into something”.
Mackrell thinks their mother’s death and their subsequent misery motivated all the siblings to leave.
“That was a really driving factor in Gwen’s career, that she had a vision of a world that was completely other than this dark, claustrophobic place of her childhood.”