I would go back and have another look at your source.
All the pit trippers and other mainline class 9 jobs we had at HM were booked to run at 35mph.
If a Class 9 train ran at 25 mph this would be shown on a BR
Form29973. This would be shown on the driver slip as a 9X
EG A train which had a mechanical shunter in tow. These engines had thier transmissions de meshed and connecting rods removed.
This 29973 would enumerate any speed restrictions on the route of the train or any other special instructions needed to work the train.
At one time class 9 trains were the norm for freight on the mainlines and I worked class 9 trains everyday for 10 years on ballast turns and pit trippers and inter regional work.

I am referring to the good old BR days of the 1960/70's era,when it was a regular thing to run "loose-coupled" trains, I thought you were referring to the same era,a time when every train had a brakevan in tow,not todays "air-braked" era with trains running about minus a brake van .Towards the end of BR in the 1990's a train that ran at a maximum speed of 35 mph was a "class 7" and I thought that "class 9's" had been abolished ? Wasn't the BR form 29973 that you mentioned also used for trains conveying "heavy axle weight" vehicles such as 100 tonne tanks ?These trains normally ran with "normal" and not "X" headcodes such as the ones I worked (6V04-6V98) we even worked a class 6(6066) which conveyed car transporters which were only "OOG" on the SR but not the LM or WR ,this was something to do with the 3rd rail.By the way when you asked me to "go back and check your source" well my source is 43 years spent as a fireman and a Driver at 21A/2E Saltley depot,and of course all the documentation and appendices issued by the BRB over these years from 1963 till 1994(when I worked for the last BR Sector/ TOC,Railfreight Distribution).

My era is Jan 28th 1981 to the present day and counting.
Towards the end of the 1980's trains with BV's on declined as the pits were all closing, all the unfitted vehicles were going to the wall, as well as the industry that we served, steel mills, ORT, newspaper trains et al.
At the end of the miners strike I had 20 pits on my route card now we have no pits to work into, just super markets.
I was on the docks at Immingham recently and the place was sinking with the weight of coal on the floor.
Not from uk pits but from China, Australia and every corner of the world.
So the need for unfitted trucks and BV's has gone forever.

I can go back further than both of you "young strappers" :D
What about 1958 onwards ? LOL.

Dont start....only having a laugh :D

48111

I can remember standing on the footbridge at Duffield and watching a freight coming along the fast line in the fifties.

Presumably the siggie had given him a run and the wagons were jumping and rocking about every which way.