On next week's BBC Antiques Roadshow, Andrew Fletcher, 45, asks for the valuation of a portrait painted of him by his former neighbour, which he received after helping Vettriano early in his career.
The two lived close to each other in a tenement in Edinburgh in 1991, and Vettriano, then just embarking on his career as a self-taught painter, asked Mr Fletcher, then a part-time student at the Edinburgh College of Art, to photograph him.
In return, the painter created the portrait of Mr Fletcher, who is now an antiques dealer specialising in 20th-century design.
Vettriano has since gone on to record-breaking success and is the subject of his own major retrospective at the Kelvingrove Art Gallery and Museum.
Mr Fletcher said: "On the Antiques Roadshow, the valuation surprised me, I thought it would be less.It a lot of money but not so much I would get nervous about keeping the painting."
Vettriano said: "I remember those early days in Edinburgh, living in the same block as Andrew, with fondness."