Artists and subject

One of the attractions at the Mylapore Festival was the chance to get your portrait sketched. That's normal. There were a few artists who would also make a caricature. All of them had enough patrons; there was a queue waiting to have their portraits - or caricatures - drawn. And then, in the midst of all those artists, was a circle of artists who were doing something that seemed quite odd. All of them were focussed on sketching just one person - what is it that they were doing? Or, who was he?