Would love to see the inside of one of these oldies!

Indeed those S&B units are still available and in use on more modern trains too. 28V was standard on BR MK.1 carriages in the 1950s as it used 14 traction cells.

That's interesting information, I used to travel by train a lot with my parents in the mid 70s- mid 80s and was always fascinated by how the lighting and electrics worked. I remember what I think were early MK2 coaches which had 4ft fluorescent tubes with opal diffusers down the centre with very noisy inverters that emitted a buzz of around 1kHz. When the train picked up speed you could here the inverter note and the light output would increase slightly as it obviously switched over from batteries to the dynamo. Many of the older trains had the tungsten lighting replaced as part of a refurb during the 70s & 80s, it made a big difference to the light levels. I almost never travel by train now, I enjoy the privacy and convenience of my car too much! The impression I get about train travel now is that its expensive, over crowded with hard seats and limited space, not particularly enjoyable.