I had rather expected somebody to come up with these by now - but as nobody else has...
Taken in 1921 by E T Miller, these images show Taff Vale A class No. 410 at the head of a train of ex-TV auto trailers, which by this date had been revamped as ordinary (!) saloon coaches. It is proably (according to John Lewis of the HMRS) the Taff's own first 6-coach corridor train (created from ex-steam rail motors and unpowered, corridor-fitted intermediate trailers) which saw a lot of service around Cardiff. (It is probably a similar daily schedule to the one reported earlier for the ex-GWR bow-ended E-set of five coaches, shown in BR days with the class 3 tank running round.) As you will see from the second image, the TV retained 2nd class throughout its existence), until the GW took over and downgraded the 2nds to thirds, although they retained the firsts, for quite some time. This were a common sight in late Taff and early GWR days. I can't remember what happened to No. 410, but most of the ex-TV auto train coaches lasted until after WW2, and many into BR days.
Large images of these, with captions, appear in Brian Miller's (no relation, apparently), book "SW Railways at the Grouping", while smaller ones, with details (and many photographs) of the ex-TV coaches appear in John Lewis' excellent "GW Auto Trailers Pt 2". Both of them are recommended reads...