The Evolution 4 is a versatile, slim-profile messenger bag that converts from a camera bag to a briefcase.  A DSLR with a lens attached, a flash, and 2 to 3 additional lenses (including a 70-200mm f/2.8) are protected inside a foam-padded compartment called the "shuttle", which features adjustable, foam-padded dividers.  To convert it to a briefcase, simply remove the shuttle from the bag using the handles.  The main compartment can then be filled with files, paperwork, or other necessary items.  Since the laptop compartment is part of the bag, a laptop can still be carried.  To convert it back into a camera bag, just slip the shuttle full of your camera gear back into the bag.