Thanks for that, Sam. It's of enormous importance within the art world because so much art is now 'derivative' work, or as the rest of us would say, 'plagiarised'. A few years ago I sought to enrol on an arts foundation course, hoping it would improve my drawing techniques. At the interview I was shocked and dismayed to learn that drawing was not part of the syllabus. Students were expected to look at photos on the internet and manipulate them to produce something they could claim as their own, preferably translating it into another medium.
In many ways, I hope the National Portrait Gallery goes ahead and sues the downloader - there are many images which are now out of copyright and which art galleries should make available so that proper artists can learn from them. I'm certain the Gallery would lose in a court of law.