Giving a helping hand -it must have been a dirty job.

The engine used as a "Pilot Engine " from Pilning up to Patchway following the passage of any freight requiring such assistance through the Severn Tunnel would have invariably been the banking engine at the rear of the train through the Tunnel itself , and 5181 displays its Banking Number on the disc so has most probably come on here in this photograph as such at Pilning.
For safety reasons eastbound freights through the Tunnel were required to have an additional brakevan at the rear with such vans being uncoupled by the banker after safe transit of the Tunnel before being worked back by that same engine to Severn Tunnel Junction for the next job.
I have read of such brakevans being described as " Enclosed Vans " , presumably with additional protection for the guard from the smoke and fumes within the Tunnel but I wonder how those fellows for such workings were selected , and whether there was any additional payment made to compensate for the health and safety hazards involved ?