Before WW1 a number of railway companies used "fish belly" wagons to transport heavy loads. "Fish belly" describes the side profile of the wagon, which becomes deeper towards the middle, so enabling the centre to carry greater loads than a similar straight-sided vehicle.
When a heavy-duty wagon was required to transport tanks during WW1 at least two types of wagons were commissioned, one of which was based upon the well established "fish belly" technology. This seems at the time to have been called a Parrot, but was later referred to as the Warflat. The other type of tank carrier was called a Rectank, (Railway Executive Committee tank wagon), and is outside of the scope of this article.
Some early photographs of Warflats show that they did not seem to have any load securing points, whereas most had six securing loops along each side. Some went to France and carried dual "WD" and "ETAT" lettering along with the painted telegraph code "PARROT" (a code name which was applied to a different type of wagon in WW2).
After WW1 a number of these wagons were sold as war surplus to the LMS, who applied fairly random fleet numbers which had previously either been unused or applied to scrapped vehicles. This cannot have occurred before 1923 as the LMS was not formed until that year.
Features to distinguish the WW1 version of the Warflat from the WW2 version include;-
an indicator plate next to the handbrake wheel, carrying the words "on BRAKE off". The handbrake wheels are off-centre and are opposite each other, with the plate between the handbrake wheel and the nearest end of the wagon;
the headstock corners are slightly rounded;
the maker's plate was centrally located and was either an oblong about 10" across or a rectangle about 6" across;
wheels were of the open spoked variety;
axlebox covers are marked "WD".
Surviving WW1 Warflat wagons seem to be rated at either 40 tons or 45 tons and include these examples;-
at a military base, fleet number WGF.8080 shows signs of former lettering "LMR" in 12" high letters;
BSC Workington, fleet numbers 831, 833, 838 and 840;
BSC Shelton, fleet number BB.3142;
BSC Shelton, fleet number BB.3161 is roughly similar to a Warflat and is mounted upon WD bogies. However, it is made of fabricated sections riveted together, as opposed to the normal pressing (or rolling ?). It may be that this is a variety of Warflat or it may be an industrial design based upon that of the Warflat.