This digital drawing, pencil and brush tools in Photoshop, could still use work; but I think a fast-ish sketch will have problems. The likeness is there - that is what I was primarily interested in achieving.
As a side note, last week I received my copy of Tom Richmonds self published book on caricature, The Mad Art of Caricature. It is unusual to find someone who can write, draw, design. The link to his informative blog is here, where you can find out more about the book.