From captions and comments on photos it appears that it was often a DWf van directly behind the loco, but I'm not finding much in the modelling convention notes or my rulebook appendix. I'm interested in whatever information people have to share, but my specific questions are
1. Were they always ordered directly behind the engine? If so, why - did the engine crew help with unloading?
2. Were the only only passenger (making it a mixed train I guess) or was it also included in goods trains?
3. When arriving at a station where there was shunting work, how quickly were they unloaded? e.g. were the take out van's brakes engaged and it was left in place while everything else was shunted around it?
4. Were they placed in a specific location for the return trip, e.g. behind the engine again