That's pretty detailed for a 'quick sketch' Kevin but it a lovely drawing. I like the way you've built up subtle gradations with a variety of marks.
Thanks Rob, I suppose quick for me would be anything under two hours. Normally I wouldn't attempt to finish a sketch like this in so short a time but when doing it with a drawing group I feel its important to finish what you started in the given time.
Oh wow ! a comment, I just love comments :) thanks very much.