This weekends model is the Vicrail ZMF brake van.
These were an oddity that was modelled on the american transfer caboose Pattern and featured a white reinforced fiber glass body module. They were designed to be converted to flat wagons with the onset of two man crewing.
Your Guards will really love you for these as they are a modern wagon equipped with cooking facilities and gas heaters for those cold frosty Mount Macedon nights.
Get them here:
http://www.megaupload.com/?d=WMD4H7BK