I guessed it would be worth a couple of hundred pounds at most, but it was a preparatory print for his famous 1639 etching The Goldweigher

My father died 20 years ago, when I was 26, and my mother died 10 years later. I’ve always felt grateful that one of the things they passed on to me was a love of art. My dad, Alan Barlow, was a stage designer, a Benedictine monk and then, after marrying my mother, Grace – who was a GP – he became a full-time artist.

In his studio in Norfolk, there were two big Victorian plan chests, where he stored paper and sketches he had created. He was also an art collector and some of the drawers contained artworks he had bought but didn’t have wall space for. For a long time, I didn’t feel ready to go through everything in his studio. I always felt connected to him when I went in there.