Didn't get the lighting quite right as was losing patience with the pen tool! Also missed some of the finishing touches and details which made the tutor's illustration stand out more. Perhaps will go back to it one day!
Instead of shading the original sketch (which was modified in Photoshop), I copied the illustration back into photoshop for rough shading to provide a more accurate outline.
Created using Illustrator Draw on the iPad Pro. Don't laugh too much! :-)