A seatpost for Brooks.
 

I have size 14 feet and on every B17 I have I have them mounted as far back as I can and wouldn't mind having just a little more adjustment on the rails. These look like a good choice.

http://store.velo-orange.com/index.p...g-setback.html

Also take a look at

http://www.rivbike.com/category-s/153.htm

This is what I use with my brooks, solid seatpost for a clyde and has the most setback.. Perfect for the B17 which has very short rails.

The VO post looks really nice.

Plain type seatpost, Brompton saddle adapter pin, and Penta clip.
the SAP is a horizontal tube when mounted , on the seat post ,
, offers a couple inches range of location. and is steel for strength,

then the saddle clip attaches to that and is rotated to be above it
Pentaclip is a stepless, mostly aluminum saddle clip, and the design is Brilliant.

I like VO's stuff. Haven't tried a seatpost yet, but I have two VO headsets, a handlebar, and a pair of stainless fenders. A teammate uses a pair of VO wheels on his brevet & commuter bike.

I've got the v/o seatpost and I like it. After using it I won't go back to a single bolt design.

The VO seatposts aren't my favorite. The shafts are undersized (with an inconsistent OD, too), the clamps can crack, and you can't get the nose of the saddle angled down properly on some frames (depending on the STA). The inexpensive Kalloy Uno that wallbike.com sells has the same setback, and works much better.

Better still, consider a Selle An-Atomica saddle as the rails allow for much more setback.

I have one of the VO seatposts on my LHT with a B17 Imperial. I prefer a two-bolt seatpost with a Brooks saddle, and the VO is a lot better looking than a Thomson (I have Thomson posts on most of my other bikes, but it just wouldn't look right on the LHT).

+1 on the two bolt clamps. The B17's are kinda touchy on the angle adjustement.