pretty well describes Brompton's P model bar brakes are on top as are the shifters..

at the bottom there is another hand grip right next to the stem.. ,
they bend outward , and upward, then bending inward again
open ends of tube is top center.
made to be set up vertically.
Available separately thru the Brompton dealers.. 1" clamp diameter, 7/8" tube
so MTB type brake levers.
pictures : http://www.sjscycles.co.uk/brompton-...b-p-prod13535/

As someone who uses Butterfly/ trekking bars.. they really are more suited
to be set up more horizontally so the hand grips are near and far ,
rather than Up and Down.

best use on My bike Mustache bars are also more a horizontal type ,
the slope in front is downward.. I have bars of each type..

of course if you have a high enough steerer tube on your bike and a threadless fork,
you can always use 2 stems and 2 sets of handlebars.

You will be asked Why?, & a lot...