Exactly; and he's hoping we name someone we got them from that he CAN sue.
Out of curiousity; does anyone know the status under English law of this type of thing? There is US case law saying that a mere photographic reproduction of a public-domain artwork does not have sufficient expressive / creative content to create a new copyright claim. However, this may not be true worldwide.
One must be aware that owners of artworks (such as the NPG) routinely claim rights under copyright law that they do not have, or at least are based on readings of copyright law that currently have no actual cases to back them up.
-Matt