There’s a theory that we all carry around in our brains a model of the ‘perfect’ human head, and that caricaturists exaggerate the elements of a face that deviate from, or ‘fall short’ of, that ideal.
Adrian often starts dealing with a new likeness by looking as much as possible at the subject, and letting a few first impressions sink in. Then, without further visual reference, he roughs out the general shape of the head, and slots the features into position. Next, he lays a sheet of thin paper on top, goes back to looking at the subject, and starts tracing his drawing, all the while refining his decisions. He often repeats the process, but looks at the head from a different angle. He might do this three of four times, but ensures he doesn’t ignore his preliminary and roughest sketch, because the first impressions are the most important. When we first meet someone, the elements of their face that deviate from the ‘mental model of perfection’ mentioned earlier are very clear to us, and the caricaturist must keep those early observations at the front of his mind.