This is a great piece. It is really refreshing to see talented artists that give realistic impression through works that aren't ridiculously impeccable (to the point where you can't tell whether it's a photomanip or a drawing). It is what drawing is all about, and it gives off personality.
This work is a contradiction in every sense. That's lovely; in some parts, your shading is stelllar -especially around the eyes- and in other parts, you make those simplistic indefinite lines like you don't care where your pencil is going. I don't know if you did it intentionally or not, but the visual effect is great.
The eyes are very intense. The fact that they are the only colored part of the work makes them almost the main protagonist of the whole drawing. Well-played there, since Hugh Laurie portrays a very intense character, a persona overflowing with passion.
For the last, I love the way you "play" with light. The shading flows from very dark tones to almost total whiteness and yet it all mixes so smoothly together to form a perfectly realistic -although in a quasi impressionistic sense- total.
You did this in 6 hours, amazing! The directions of the shadings look consistent and the highlights on the face are well placed. The clothing also has a consistent hue that doesn't show any lines from over sharpened pencils etc. Well done.