I get asked to contribute artworks to charity auctions or do a drawing for a worthy campaign about once a week. Sometimes artists are seen as being able to print money. I give to quite a lot of them but I can suffer from charity fatigue. I am always delighted, though, to contribute to the RCA Secret show, now in its 15th year, in which artists donate postcard-sized works anonymously, and all are sold for £40 each. The money goes into a bursary fund to help to support the RCA's fine-art students.

Keeping the works anonymous is a very clever idea because potential buyers have to use their own powers of discrimination. They cannot rely on brand names for validation. They must look at the artworks closely rather than read the labels, a habit I suggest that they might find rewarding at any exhibition. I have contributed a few cards for the past five years. I don't go out of my way to disguise my works as I think it is nice for the buyers to have a characteristic drawing.

Giving artworks to good causes highlights the artist's ability magically to transform cheap materials into something worth money. I call this gift/curse Picasso Napkin Syndrome (or PNS) after Pablo's habit of paying for meals with a doodle. One aspect of having the Midas-like touch of PNS is that I find myself agonising over a tiny, seemingly inconsequential, drawing because there is the strong possibility that at some point it is going to be in the focus of the public eye. Creativity demands a relaxed fluency but I find my artistic sphincter nipping up at the thought that some casual scribble of mine will be exposed to the scrutiny of connoisseurship or be judged harshly in the saleroom. So I stare pathetically at the blank postcards with all the intensity of Michelangelo, chisel in hand, squaring up to a block of marble.

Sadly an artist's ability to transform base cardboard into gold can attract scammers. Shortly after RCA Secret one year I received a letter from a woman saying that she had queued for the sale with her autistic son. Her son, she said, was a great fan of my work and he was bitterly disappointed that they were unable to secure one of my postcards. She sent me some of his repetitive scribbles as evidence of his condition and his love of art. She asked if I could find space in my heart for her son and do a drawing just for him. I'm an innocent soul and I was touched. My heart curiously hardened when a few days later I received a near identical letter from a different name and address.

I thought that someone with the ability to come up with such an elaborate scam should do well as a contemporary artist.

RCA Secret is at the Royal College of Art, London SW7. Viewing: Nov 14-21, then sale day Nov 22 from 8am. Free admission. 020-7590 4186, www.rca.ac.uk/secret

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