There's a story about that 21ft brake van. My brother Bob used to walk to Bletchley station every day and noticed a lump sticking out of the side of an old house he passed. It looked like a Guard's lookout from a carriage. Eventually he called at the house and it turned out to be an LNWR 21ft passenger brake van. The carriage expert Philip Millard couldn't tell us much about it, so over several visits we photographed and measured it in great detail, producing and publishing drawings from which that kit and others were made.
One side was against the house (which was thatched), one end had shiplap boarding over it. A pitched roof was over the top. The owner was a modeller, making a large scale r/c model tank at the time, so was understanding of these two cranks knocking at his door and very helpful. A few years later the roof needed attention, so while some of the tiles were off we managed to gain access to measure and photograph the top of the roof too.
The house has changed hands since and the lookout has been removed, but I've not been past it for several years. Just goes to show, if you see something that looks interesting have a proper look and record it in great detail. You can never have too many photographs and don't under-estimate the number of visits required to measure it all properly because when you get home and start to draw it up, there's always a vital measurement you forgot or something that doesn't fit!
Mike