One thing the Midland did well was use standardised bits and adapted them as they went along. This is quite noticeable in their signal boxes but also in their brake vans and, visually at least, the evolution is pretty obvious and logical.  So from left to right…
So starting with the early midland 10 ton van.  This was very much of its time and featured 3ft 6in wheels with a veranda at one end only. The open platform thats so familiar to the idea of a brake van wasn’t something that the Midland really went with and only one lot (D2096) of 4 vehicles would feature this in the future.  The rest of standard Midland brake vans would all feature a full length roof.

The later 20 ton van was built to diagram 1659 between 1924 and 1927 and featured a longer 12 ft wheelbase with 3ft wheels and a cabin that was 13ft 4in inside. This would become the standard size cabin for the rest of the midland vans that followed The similarities between the 2 type shown are pretty obvious with vertical planking and basically the same end panels.

Next came diagram 1657 (the diagram numbers don’t seem to follow in a chronological order) built between 1927 and 1931.  The obvious change was the duckets on the side.  The outer ends also evolved to feature a smaller opening and flush planking but still with the same offset central vertical spar.

From diagram 1657 to diagram 1940 built in 1933/34.  Virtually identical except for an increase in wheelbase of 14ft which resulted in a visually less nicely proportioned vehicle. It’s suggested that the increase was an attempt to improve stability at higher speeds.

On to diagram 1890 also built in 1933/34.  Still 20 tons but with another wheelbase increase to 16ft and an increase on overall length from 20ft to 24ft. The cabin size remained the same but there was a change from vertical to horizontal planking. Note the end central spar now really is central!

Finally diagram 2036.  Basically the same as before but with the door opening moved to the far end.  The planking on the ends is now gone as is the central spar as well as the upper part of the opening following the roof line. There were a few slightly different variants of this design such as diagram 2068 (the last being built in 1950) which featured a deeper ballast box between the wheels. Some of this last batch were also fitted although many of the other types were through piped at times in their lives.