The photographer Stuart Heydinger was my colleague on the Observer in the 1960s when I was picture editor. To illustrate a feature written by Neal Ascherson about the growing movement for Scottish independence, I sent Stuart to northernmost Scotland to photograph the SNP-supporting provost of Wick, William Dunnett.

He was an engine driver who had just brought a train up from Inverness, so Stuart photographed him in his working clothes – overalls, denim tunic and plastic-topped British Rail cap – standing on the stairs of the town hall in front of a large oil painting of Sir John Sinclair of Ulbster (1754-1835) in full Highland regalia.

It was a brilliantly imaginative juxtaposition and when Stuart brought a contact sheet up from the darkroom there were about six perfect shots on it, taken with his Rolleiflex, using the natural Caithness light from the landing window.

When I asked if there were any more, he said: “No. I knew I’d got him with that lot.” There was nothing I could say, except: “Well done.” This was at a time when most photographers took enough shots to fill four to six contact sheets.